Most people are probably aware of the Urban Heat Island (UHI) Effect, i.e. the phenomenon whereby large urban areas are warmer than the surrounding countryside, often by a significant margin.

For some time, sceptics have questioned whether the increasing urbanisation of the planet (and the inevitable urbanisation of some previously rural locations where temperature gauges are located) might create an inaccurate impression as to the extent to which global temperatures are rising. In other words, if temperatures are increasing due in part to urbanisation, might not the claims as to rising temperatures be overdone, and perceived rising temperatures in fact be due more to urbanisation than to rising temperatures per se?

One answer to this question has always been that those responsible for maintaining temperature records carry out adjustments to reflect the impact of the UHI, and that sceptic worries in this regard are unjustified.

A very important tool in the armoury of climate warriors who seek to dismiss suggestions that UHI has any impact on claims of rising worldwide temperatures, is this paper:

“Assessment of Urban Versus Rural In Situ Surface Temperatures in the Contiguous United States: No Difference Found” by Thomas C Peterson, the print edition of which was published on 15th September 2003.i

I think his main conclusion is that stated at the end of the admirably short opening abstract:

Contrary to generally accepted wisdom, no statistically significant impact of urbanization could be found in annual temperatures. It is postulated that this is due to micro- and local-scale impacts dominating over the mesoscale urban heat island. Industrial sections of towns may well be significantly warmer than rural sites, but urban meteorological observations are more likely to be made within park cool islands than industrial regions.

In arriving at this conclusion, Peterson relied on adjustments that in his view eliminated any risk of UHI bias. Quoting again from the abstract:

All analyses of the impact of urban heat islands (UHIs) on in situ temperature observations suffer from inhomogeneities or biases in the data. These inhomogeneities make urban heat island analyses difficult and can lead to erroneous conclusions. To remove the biases caused by differences in elevation, latitude, time of observation, instrumentation, and nonstandard siting, a variety of adjustments were applied to the data. The resultant data were the most thoroughly homogenized and the homogeneity adjustments were the most rigorously evaluated and thoroughly documented of any large-scale UHI analysis to date.

Even five years ago, Peterson’s 2003 paper had been cited approvingly 285 times. And no wonder. If UHI is a stick with which sceptics try to beat climate warriors, then Peterson has provided a very useful shield to defend against those attacks.

Let’s look at that main conclusion again:

Contrary to generally accepted wisdom, no statistically significant impact of urbanization could be found in annual temperatures.

It’s quite a claim, going as it does against what most people instinctively feel and experience, as well as well as contradicting “generally accepted wisdom”. By the time Peterson wrote his paper in 2003, there had been many studies looking into UHI, and in fairness to him, in arriving at his conclusion, he references a great many of them (below). Having read their conclusions, however, (as set out in Peterson’s paper) I struggle to arrive at the same conclusion as Peterson.

Earlier UHI papers

Cayan and Douglas (1984) found urban-affected heat island temperature increases of 1°–2°C common when comparing linear trends over three to five decades of urban stations with trends at non-urban sites.

Kukla et al. (1986). They looked at the difference in trends between rural and urban data over a 40-yr period for 34 station pairs and concluded that the urban contamination amounted to about 0.12°C decade.

Two different approaches were used by Karl et al. (1988) in an attempt to determine the effect of urbanization on the U.S. climate record. Average annual temperature was found to be 0.11°C warmer in cities of 10, 000 people, 0.32°C warmer in a 100, 000 population city, and 0.91°C warmer in a 1, 000, 000 population city. All of the warming in average temperature comes from minimum temperatures as their annual assessment of daily maximum temperatures indicates that urban sites tend to be cooler than rural during the warmest part of the day.

Using 42 pairs of urban–rural stations in China, Wang et al. (1990) found an average urban heat island of 0.23°C

Gallo et al. (1993) looked at clusters of stations and compared the relationship between the difference in rural and urban temperatures and a vegetation index. Most but not all of their rural–urban differences showed urban stations as warmer.

China’s northern plains were the subject of a UHI analysis by Portman (1993). Using data from 1954 to 1983 and examining how the differences of residuals between each urban station and every rural station changed, the author determined that the mean annual urban warm bias increased 0.19°C during these 30 years.

An analysis of the Barcelona heat island is presented in Moreno-Garcia (1994). In addition to transects, the author examined data from two stations. On an annually averaged basis, the urban site was 0.2°C cooler for daily maximum temperatures and 2.9°C warmer on minimum temperatures. It was noted that the two stations had the same instrumentation, similar elevations, and “similar” distances from the sea

The San Antonio, Texas, heat island was assessed by Boice et al. (1996) using 45 years of data from one San Antonio station and three stations from surrounding small towns. The results indicate that San Antonio’s minimum temperature increased at an average rate of 0.3°C relative to the other stations.

Todhunter (1996) determined that the Minneapolis–St. Paul mean urban heat island in 1989 was 2.1°C.

Using data from three different parts of the world, Camilloni and Barros (1997) determined that the urban–rural temperature difference decreases during periods when rural temperatures are increasing and increases when rural temperatures are decreasing.

Böhm (1998) used data from three urban, three suburban, and three rural stations to examine the Vienna, Austria UHI. He found that the urban effect is strongly influenced by local surroundings and therefore could not be regarded for the city as a whole, with the magnitude varying from 0.2° to 1.6°C. The trend in urban warming varied as well, with two central city stations showing no increase in urban warming while the third had 0.6°C warming in 45 years. In Vienna, the average UHI effect was found to be strongest in winter.

Data from two stations were used by Magee et al. (1999) to determine that the effect of the Fairbanks, Alaska UHI grew by 0.4°C over a 49-yr period, with winter months experiencing a more significant increase of 1.0°C.

An analysis of surface air temperature compared to 0.91-m-deep soil temperature indicated a UHI increase of 0.2°C over the period 1889–1952 for Urbana–Champaign, Illinois (Changnon 1999).

Gallo and Owen (1999) identified clusters of stations in the contiguous United States and compared the relationship between the difference in rural and urban temperatures and a vegetation index. They found seasonal changes in the urban–rural differences that tracked changes in the vegetation index. Most, but not all, of their rural–urban differences showed urban stations as warmer with urban stations averaging 0.38°C warmer than rural.

One city, Tucson, Arizona, was the subject of several different analyses by Comrie (2000), including transects by vehicle-mounted thermistors, spatial examination of in situ data, and comparison of rural and urban temperature time series. The results indicated that Tucson’s UHI warming was ∼3°C over the last century and >2°C of this occurred in the last 30 years.

Using 20 years of data from one urban station and three rural airport stations, Morris et al. (2001) determined that Melbourne’s nocturnal UHI was 1.13°C.

One rural and one urban station were used by Kim and Baik (2002) to determine that Seoul warmed 0.56°C relative to its rural neighbour during the 24-year period 1973–96.

Kalnay and Cai (2003) compared data from 775 urban contiguous U.S. (CONUS) stations with 167 rural stations and found that the urban warmed 0.18°C more than the rural during the 1980s and 1990s.

In fairness, 2 or 3 reports cited by Peterson did not conclude there was a UHI effect. Basically, however, it seems that the weight of scientific evidence, before Peterson 2003 was published, was firmly on the side of there being a substantial UHI. It was the result of numerous studies over lengthy time scales from sites all over the world. Not good news for global climate alarmism. No wonder Peterson has been cited so often since his report emerged!


If the previous research so clearly supported claims that temperature measurements are being distorted by UHI, how did Peterson manage to conclude differently?

Peterson’s dismissal of the earlier studies relied on adjustments to iron out other factors which he claims contaminated the measurements, thereby distorting the temperatures as recorded, and in effect artificially introducing an otherwise non-existent UHI:

Specifically, careful attention will be paid to adjusting the data to account for the natural effects due to differences in elevation and latitude as well as the artificial effects due to differences in time of observations, differences in instrumentation, and the effects of non-standard siting practices, namely, rooftop installations. Once the data are adjusted for these factors, it will be possible to accurately assess the impact of urbanization on the climate record.

Which is fair enough, so far as it goes, but his data, whilst selected carefully to avoid missing data etc., was very limited:

Quality-controlled mean monthly temperature data for U.S. in situ stations were obtained from the National Oceanic and Atmospheric Administration/National Environmental Satellite, Data, and Information Service/National Climatic Data Center (NOAA/NESDIS/NCDC) archives. The analysis period selected was the same one used by Gallo and Owen (1999), the three years 1989–91. Ending the period in December 1991 allowed the analysis to avoid the confounding influence of the Automated Surface Observing System (ASOS) deployment, which started in 1992. Three years is long enough to produce robust means. A longer period would increase the problem of missing data.

In other words, three years of data from the contiguous US only, provided by sources that not everyone would regard as unbiased or disinterested, was used to overturn decades of research from all over the world, from a variety of data providers.

Also, the way in which rural, urban and suburban are defined might surprise a non-American:

Satellite night-light data are the latest tool used for determining which stations are rural and which are urban. For example, while Hansen et al. (1999) use map-derived rural/urban metadata in their global temperature analyses, Hansen et al. (2001) moved up to satellite-derived night-lights rural/urban metadata. The rural/urban classification metadata used in the analysis presented here was developed by Owen et al. (1998) using night-light data from the Defense Meteorological Satellite Program-Operational Linescan System. Their methodology divided 1-km2 grid boxes throughout the United States into urban, suburban, and rural classifications… Advantages of the Owen et al. metadata include that they are objective (while map based is often subjective) and that night-lights, in the United States at least, are good indicators of urbanization whether residential or industrial. Owen’s et al.’s urban grid boxes had an 84.4% agreement with data from the U.S. Bureau of the Census (1997).

The method used had an 84.4% agreement with data from the US Bureau of the Census – or to put it another way, disagreement of 15.6%. Am I alone in thinking that’s quite a high level of disagreement?


The stations consisted of 40 clusters of stations well distributed around the country with a total of 289 stations (see Fig. 2). The Owen et al. (1998) methodology classified 85 of these stations as rural, 191 as urban, and 13 as suburban.

For example, the Global Historical Climatology Network (GHCN; Peterson and Vose 1997) consists of over 7500 temperature stations around the world that were identified as rural, urban, or an in-between class of small town using information on operational navigation charts and a variety of different atlases. A rural station was any station not associated with a town of over 10, 000 population.

Personally, I think this contaminates his ultimate findings without more ado. It’s not scientific, but living in a rural location (some 3 miles from where I now live, and at the same altitude) I have little doubt that it was distinctly colder than where I live now, in a small town, with a population probably a little under 10,000 (which Peterson would therefore categorise as a rural location). I can’t prove it, but it feels as though it’s the case.

Peterson’s basic conclusion is that once adjustments are made for inhomogeneities, the UHI effectively disappears from the record. In fact, in some respects Peterson goes even further:

Some of the largest cities in the United States were not represented in the 40 clusters. Could the large cities be showing urban warming while the smaller ones do not? To answer that question, the mean urban minus rural temperature difference was calculated for each cluster. An assessment of five of the largest cities—Boston, Massachusetts; Dallas, Texas; Detroit, Michigan; Salt Lake City, Utah; and Seattle, Washington—found that one (Detroit) did not have adequate rural and urban data to be analyzed while all of the rest had homogeneity-adjusted urban temperatures that were cooler than the homogeneity-adjusted temperatures of their rural neighbors.

Here he is actually saying that by the time the adjustments have been made, the countryside is proved to be warmer than cities! Does such a conclusion not ring alarm bells, and undermine the reasoning behind the adjustments? Am I alone in finding this to be a truly astonishing conclusion, apparently accepted by the “consensus” without demur?


Peterson justifies his findings, despite the numerous studies whose results have to be explained away, by pointing out that the studies in question failed to discuss or address inhomogeneities. Such inhomogeneities would include a wide range of factors which possibly skew results over a period of time, the main ones being changes in location (whether of latitude, longitude or elevation); changes in observing practices (probably those of greatest concern being changes in the time of once-daily observing and resetting of maximum and minimum thermometers); and changes in instrumentation (the change from one type of thermometer to another can cause an artificial warming or cooling in the data).

He observed that attempts to deal with these issues can themselves be problematic:

The data are inhomogeneous so they need to be adjusted. Yet if the adjustment technique can successfully identify and account for a discontinuity caused by changing from one thermometer to another, the techniques may well identify and compensate for abrupt changes associated with urbanization such as paving nearby grass. Therefore, the inhomogeneity of the data and the approaches to compensate for the inhomogeneities can have strong impacts on assessments of the UHI’s effect on in situ observations.


What Adjustments are Made to Account for Inhomogeneities?

One of the main temperature datasets is maintained by the National Oceanic and Atmospheric Administration (NOAA) in the USA. NOAA’s websiteii is helpfully transparent in this regard, thus helping us to get a handle on the adjustments made. As the introduction to the relevant page on the website makes clear:

There are several factors that are important in monitoring global or U.S. temperature: quality of raw observations, length of record of observations, and the analysis methods used to transform raw data into reliable climate data records by removing existing biases from the data.

Interestingly, NOAA’s website suggests that the main biases for which adjustments need to be made are those relating to sea surface temperatures and in respect of the shift in land-based temperature measurements from afternoon to morning readings. Both biases, and the need for adjustments to be made in respect of them can readily be appreciated. Clearly afternoon readings will generally give a higher temperature than morning readings taken at the same location. If, as seems to be the case, the practice in the US has changed from afternoon readings to morning readings, then without an adjustment, an incorrect perception of cooling could be obtained. I have no problem with an appropriate adjustment being made to reflect that. Similarly, with regard to sea surface temperature measurements:

The most important bias globally was the modification in measured sea surface temperatures associated with the change from ships throwing a bucket over the side, bringing some ocean water on deck, and putting a thermometer in it, to reading the thermometer in the engine coolant water intake. The bucket readings used early in the record were cooler than engine intake observations so the early data have been adjusted warmer to remove that bias. This makes global temperatures indicate less warming than the raw data.

So far so good. What, then do NOAA have to say about UHI adjustments? Surprisingly little:

We identified which GHCN stations were rural and which were urban. Then we created global temperature time series from the rural only stations and compared that to our full dataset. The result was that the two showed almost identical time series (actually the rural showed a little bit more warming) so there apparently was no lingering urban heat island bias in the adjusted GHCN dataset.

This is another defence against allegations that UHI wrongly influences the claims of warming. Essentially, the argument is that if both urban and rural sites show roughly similar warming trends, then the direction of travel of global temperatures is being fairly represented in the statistics. UHI is not artificially increasing the temperature increase. And that is an argument that I can comprehend and accept.

A similar argument is made by Jones et al. in “Urbanization effects in large-scale temperature records, with an emphasis on China” (2008)iii

Global surface temperature trends, based on land and marine data, show warming of about 0.8°C over the last 100 years. This rate of warming is sometimes questioned because of the existence of well-known Urban Heat Islands (UHIs). We show examples of the UHIs at London and Vienna, where city center sites are warmer than surrounding rural locations. Both of these UHIs however do not contribute to warming trends over the 20th century because the influences of the cities on surface temperatures have not changed over this time. In the main part of the paper, for China, we compare a new homogenized station data set with gridded temperature products and attempt to assess possible urban influences using sea surface temperature (SST) data sets for the area east of the Chinese mainland. We show that all the land-based data sets for China agree exceptionally well and that their residual warming compared to the SST series since 1951 is relatively small compared to the large-scale warming. Urban-related warming over China is shown to be about 0.1°C decade over the period 1951–2004, with true climatic warming accounting for 0.81°C over this period.

Do these arguments still hold good in 2021?

How Hot Are Urban Heat Islands Today?

Over the last few years, and with increasing shrillness, I have noticed more and more claims that the UHI Effect is very significant indeed. Ironically perhaps, it’s often the likes of the Guardian who make these claims, usually in the context of saying that in effect poor (often BAME) residents of such areas are suffering more from heat waves than are wealthier (often white) people living in the less-affected leafy suburbs. For instance, a recent articleiv in the Guardian stated:

Much of this variability can be traced back to racist housing practices, which concentrated people of color in neighborhoods lacking cooling, green space and tree shade. On a hot day, a neighborhood with little shade can be up to 20F hotter than a more affluent and greener area in the same city.

In fairness, the article doesn’t claim that the UHI is generally quite so extreme, but it does say:

The sweltering heat endured by major American cities is being fueled by vast swaths of concrete and a lack of greenery that can ratchet up temperatures by nearly 9F (5C) compared with surrounding rural areas, new research has found.

It goes on to provide a handy table setting out which US cities are suffering most from UHI effects, with New Orleans at the top at 8.94F down to seven cities (out of 20) tied on 6.97F

The Mayor of London/London Assembly websitev makes similar claims about London:

A changing climate and higher average temperatures combined with increasing urban development and densification is resulting in London getting hotter.

London is experiencing hotter and drier summers that are further impacted by the Urban Heat Island effect (UHI). The UHI can cause London to be up to 10C warmer than neighbouring rural areas. This is a result of the sun’s rays being absorbed by hard surfaces rather than by vegetation such as trees, plants and grass. Radiation from our hard surfaces is released into the air as heat. The UHI reduces the ability for cities to cool and impacts on our own capacity to regulate temperature.

It doesn’t seem to have occurred to those at the Guardian (and elsewhere) who make these claims, that they are simultaneously undermining their claims regarding global warming, and the “climate crisis” since if UHI is as significant an issue as they now claim, then it opens up once more the whole debate as to the impact of UHI on temperature and warming claims. If the UHI Effect is big, and getting bigger, are the adjustments made by the guardians of the temperature records still sufficient? And if they aren’t, then can we trust the claims of a rapidly warming world? Is the reality just one of rapidly warming urban heat islands?

Urban Flooding

It isn’t just heat. Cities increasingly seem to be suffering from flooding. Of course, this too is regularly being attributed to climate change, for instance in this article in the Guardian: “Flash floods will be more common as climate crisis worsens, say scientists”:

Sadiq Khan, the mayor of London, said his powers were limited on flood defences, but he was dealing urgently with Thames Water on the issue. “We are seeing increasing incidents of extreme weather events linked to climate change,” he said. “This is not the first time in recent weeks that London has been hit by major flooding. Despite having limited powers in the area, it remains a key priority for myself and London’s council leaders that more is done urgently to tackle flooding and the other impacts of climate change. This includes continuing to urge Thames Water to address localised issues with infrastructure that may exacerbate the impact of flooding.

So it’s all down to climate change, then? Maybe, maybe not. Maybe it’s more to do with urbanisation? Interestingly, the BBC ran an articlevi at around the same time as the Guardian, and if one persists far enough, a different story potentially emerges:

Dr Veronica Edmonds-Brown, senior lecturer in aquatic ecology at the University of Hertfordshire said London’s Victorian era drainage system “cannot cope with the huge increase in population”.

Dr Edmonds-Brown said there were several reasons for Sunday’s flooding.

The first is building on the floodplains of the Thames and River Lea. The second is urbanisation. The more impervious surfaces we install – and we are amid a rapid housing programme at the moment – the worse this situation will get.

The final reason is that our drainage system is not built for the amount of water it is receiving. Due to budget limitations, local authorities are not able to maintain or improve them.”

An articlevii on the website of Japan For Sustainability also suggests that flooding as a result of localised downpours might itself be a function of the UHI, rather than of climate change:

The UHI effect…causes serious weather events such as localized torrential rains. Recently, urban areas in Japan including Tokyo have experienced more incidents of unpredictable, torrential rains, called “guerrilla downpours;” one such event this year caused an accident in which workers in an underground sewage system were swept away and drowned.


UHI phenomena can occur any place with a concentrated population where countermeasures are not being taken. Problems caused by the UHI effect are becoming a common concern among big cities around the world, including those in developing countries.

In the last few days, those well-known climate scientists, Zurich Insurance, have warned, according to the BBC’s Roger Harrabin,viii that proposed planning reforms in the UK, which could make it easier to convert shops into houses and apartments, might lead to more people “suffering from potentially deadly heatwaves”. Not just heatwaves either – floods too. Why?

Well, sloppy thinking prevails. They warn of people suffering from climate change, but the article then says:

It warned that many properties in built-up areas were affected by the “urban heat island” effect, where temperatures are hotter than outlying areas. It added these properties were also at risk from flash floods caused by heavy downpours on concrete surfaces.

Not climate change then. As with increasing heat, it’s a problem of urbanisation. What, then are the trends with regard to urbanisation?


What follows is a limited tour d’horizon, and I cheerfully admit using Wikipedia as a ready source.ix According to it:

It is predicted that by 2050 about 64% of the developing world and 86% of the developed world will be urbanized. That is equivalent to approximately 3 billion urbanites by 2050, much of which will occur in Africa and Asia. Notably, the United Nations has also recently projected that nearly all global population growth from 2017 to 2030 will be by cities, with about 1.1 billion new urbanites over the next 10 years.

According to Wikipedia, urbanisation brings costs and benefits, both to individual health, and to the planet. Although healthcare is often better in urban areas, especially in developing countries, less active lifestyles can lead to increased obesity, and rapid unplanned flight from rural areas to cities can lead to the growth of slums and shanty towns. In some countries, urban areas are also often much more prone to violence and drugs.

Environmentally, some argue that urbanisation is beneficial, for example by leading to reduced birth rates and a reduction in “slash and burn” farming methods. On the other hand:

However, existing infrastructure and city planning practices are not sustainable. In July 2013 a report issued by the United Nations Department of Economic and Social Affairswarned that with 2.4 billion more people by 2050, the amount of food produced will have to increase by 70%, straining food resources, especially in countries already facing food insecurity due to changing environmental conditions. The mix of changing environmental conditions and the growing population of urban regions, according to UN experts, will strain basic sanitation systems and health care, and potentially cause a humanitarian and environmental disaster.

In the long-run, urbanisation looks set to continue, possibly at an increasing rate. This is a remarkable prospect, given that we already have a situation where the population of the world’s largest city (Tokyo), at 37-39 million (depending on how you define it) is around the same as the population of the whole of Canada.


I’m not a scientist, and I certainly don’t seek to argue that climate change isn’t happening. I do, however, ask some questions, and seek some balance in the debate. I suspect that in an increasingly urbanised world, urbanisation may be causing as many problems as are caused by increasing greenhouse gas emissions. I wonder if UHI temperature adjustments are adequate to deal with the significantly increasing urban temperatures. And finally, I think all this points to the need to concentrate on adaptation rather than mitigation. In cities in particular, there are steps that can be taken to minimise the impact of UHI. It is my belief that, in a world where financial resources are limited, and Governments’ budgets are already strained by the impact of the Covid pandemic, money would be better spent on taking those (adaptation) steps than on attempting, futilely, to reduce greenhouse gas emissions.











  1. Mark, thanks for the thorough analysis. My little contribution is to cite the definition of a Class 1 site according to the World Meteorological Organisation:

    Class 1
    (a) Flat, horizontal land, surrounded by an open space, slope less than ⅓ (19°);
    (b) Ground covered with natural and low vegetation (< 10 cm) representative of the region;
    (c) Measurement point situated:
    (i) At more than 100 m from heat sources or reflective surfaces (buildings, concrete surfaces, car parks, etc.);
    (ii) At more than 100 m from an expanse of water (unless significant of the region);
    (iii) Away from all projected shade when the sun is higher than 5°.

    This defines the cream o' the crop. Anything else is not telling you what the climate is doing.


  2. Jit, thanks for that. I wonder how many “record-setting” sites comply with the criteria?


  3. Thanks for that, Mark. The UHI effect is something of a battleground that deserves a considered approach. Data homogenisation is a very tricky practice. I know that Steven Mosher has strong views on this subject, particularly in respect of the ‘micro and local-scale impacts’. It would be nice of him to comment. For my part, I struggle to understand the subject since I can’t get my head around the arbitrariness of some of the definitions, e.g. what constitutes ‘urban’.


  4. “Weatherwatch: Cardiff taps into its subterranean heat
    Pioneering scheme in Welsh capital uses groundwater boreholes to take advantage of urban warmth”

    “The air in urban areas can be up to 3C (5.4F) warmer than in the surrounding countryside, known as the urban heat island effect. But less well known is that urban heating also warms the ground, and could be used to help combat the climate crisis.

    A lot of this extra urban heat goes into the ground from basements, underground car parks, heat from sewers and much else, and a pioneering scheme in Cardiff is tapping into this subterranean heat. The Welsh capital has dozens of boreholes about 10 metres deep filled with groundwater, and a survey by the British Geological Survey (BGS) found that between September and December water in these boreholes can reach 16C while water nearer the surface can be close to or below freezing.

    This warmth can be tapped using ground source pumps to use for heating homes and other buildings; in one trial a heat pump was installed in a borehole at a nursery school in Cardiff, and the nursery now only needs to turn on its gas heating on the very coldest of days.”

    I lack the skills to know how practical this is, but in principle it actually seems like a good idea. Still, it’s curious how the UHI varies from article to article. Today, it’s “up to 3C (5.4F)”.


  5. “”Floods: Research shows millions more at risk of flooding”

    “A new study shows that the percentage of the global population at risk from flooding has risen by almost a quarter since the year 2000.

    Satellite images were used to document the rise, which is far greater than had been predicted by computer models.”

    Perhaps the models aren’t that good, then, and should be ditched?

    “The analysis shows that migration and a growing number of flood events are behind the rapid increase.

    By 2030, millions more will experience increased flooding due to climate and demographic change, the authors say.”

    The report can be found here:

    Here’s the bit the BBC missed out:

    “Investing in flood adaptation strategies may reduce the loss of life and livelihood caused by floods. Where and how floods occur and who is exposed are changing as a result of rapid urbanization, flood mitigation infrastructure and increasing settlements in floodplains. Previous estimates of the global flood-exposed population have been limited by a lack of observational data, relying instead on models, which have high uncertainty.”

    There’s our old friend (or should that be enemy?) again.

    And there’s more:

    “An estimated $651 billion (USD) in flood damages occurred globally from 2000 to 2019. Investments in flood adaptation reduce mortality and asset losses. Yet, only 13% of disaster funds are allocated to preparedness, mitigation and adaptation.”

    And there’s this:

    “One study estimates that population growth in 100-year floodplains (areas with a 1% annual flood probability) outpaced total population by 2.6% from 1970 to 2010 in 22 countries.”

    And this:

    “Studies enabled by global flood models reveal trends including declines in loss of life and reduced property damage when controlling for hazard size. Sub-Saharan Africa is the only region with increasing flood mortality rates since 1990, where urban flooding has been growing and is expected to continue to do so.”

    In fairness, McGrath does bring himself to say “In European and North American nations, the risk was stable or decreasing.” Though you have to read quite a long way beyond the headline to find it.

    He can’t resist working the climate change article, but he does also say this:

    “One of the puzzling aspects of the research is why people in many countries are moving into flood prone areas rather than away from them.

    While the global population grew by over 18% between 2000 and 2015, in areas of observed flooding, the population increased by 34%.

    Dr Tellman says that one aspect of this growth is related to climate change, which is changing the locations of flood plains to encompass more people. But economics also plays an important role.

    “Places that have flooded tend to be really cheap land for informal development, so in Guwahati, India, and Dhaka in Bangladesh, we see people moving in, and so flooded areas then become settled,” she said.

    “It may not be people’s choice to live in those areas because they might not have a lot of agency. If there were really good public housing programmes or other options, I think people probably wouldn’t choose to settle in a hazardous area.””

    Climate crisis or an urban and public policy crisis?


  6. “Olympic athletes and volunteers in Tokyo ‘tortured’ by hottest Games ever
    Hottest Olympics in history will put pressure on organisers to rethink sport in light of climate crisis”

    Except that it’s nothing to do with climate change, as even the Guardian implicitly acknowledges if you read on far enough:

    “It a far cry from the “mild and sunny weather” that the Tokyo bid committee had promised in 2013 as “an ideal climate for athletes to perform at their best”. They should have known better. As early as 1964 – the last time Tokyo hosted the Olympics – organisers were wary enough of the summer heat to schedule the Games in October.

    Since then the city has been getting hotter. Temperatures have risen by 2.9C since 1900, according to Nasa. almost three times the global average. This is largely because the city has been encased in so much concrete that warm air gets trapped, leading to an “urban heat-island effect”.”

    Liked by 2 people

  7. My memory is now not to be relied upon, yet I seem to remember that climate change models predict that much of any temperature increase would occur in the winter making them milder, and not during summer months. Yet day after day, week after week climate change specialists working and writing at the Guardian, BBC and Channel 4 attribute every heatwave and wildfire, wherever they occur, to climate-change enhanced temperatures during summer months. What gives?

    Liked by 1 person

  8. Alan, milder winters don’t sell panic (quite the contrary), but hotter summers spell climate chaos, and therefore provide panic-inducing headlines. Don’t you know there’s a last chance saloon COP starting in less than 3 months’ time? Do keep up!


  9. Alan: There were two things I was told about warming at my mother’s knee (or so it feels now, it’s so long ago):

    1. As you say, warmer mostly applies to winters
    2. Warmer also mostly applies to higher, colder latitudes, reducing the differential with the equator.

    And that last one was expected to reduce the intensity of storms.

    But now we know better.



  10. Richard,

    Whatever transpires, there will always be a scientist available to say that the science has moved on. Each failed prognosis is an opportunity to point towards fabulous advances. But it’s a bit like Fairy Liquid. It has been improved so many times over the years that, when you look at its current performance, you have to wonder how shit it must have actually been at the outset.

    Liked by 1 person

  11. Now don’t go bad mouthing Fairy Liquid. It now comes in various colours (perhaps to match various kitchen decors) but, like climate sensitivity, has barely changed over the decades. Use the recommended amounts and scarcely a bubble, use the tiniest bit more and a bubbleverse. 278 ppm = Nirvana, any increase = Armageddon.

    This is the washed up theory of climate change.

    Liked by 3 people

  12. John:

    you have to wonder how shit it must have actually been at the outset


    like climate sensitivity, [Fairy Liquid] has barely changed over the decades

    The thing is, Jule Charney’s Report in 1979, with its statement of gratitude to Richard Lindzen at the start, was honest shit. 42 years later we have much worse shit (in the highly improbable guise of no progress) made out to be beautiful perfume. At least till tomorrow, when the official range of possible climate sensitivity may be changed. You never know.


  13. Given the push the Guardian has made recently regarding the extra heat in cities, and the disproportionate effect that heat has on disadvantaged people, this seems a little odd, to say the least:

    “Denser cities could be a climate boon – but nimbyism stands in the way
    Drawing people into cities could cut emissions and combat housing crises. But even progressives are hard to convince”

    “Climate scientists and urban planners increasingly suggest that one of the most impactful ways to slash greenhouse gas emissions is to make cities denser. This change, scientists have calculated, is even more impactful than installing solar panels on all new constructions or retrofitting old buildings with energy-saving technologies. Residents of cities like San Francisco, Chicago, New York and Minneapolis already have much lower carbon footprints than in the surrounding suburban sprawl. City dwellers tend to have smaller apartments that require less energy to heat and cool.”

    Lower carbon footprints, maybe; but hotter and less comfortable, surely? Isn’t that what the Guardian has been telling us, or do I misunderstand? Or do we have to sacrifice comfort and put up with terrible urban heat in order to save the planet?


  14. Don’t include SanFrancisco in your list for the reasons you specify. Rather it’s the afternoon and evening fog rolling in that acts as a natural air conditioner. After all, Mark Twain quipped “The coldest winter I ever spent was a summer in San Francisco “


  15. “Nearly 25% of world population exposed to deadly city heat
    Concrete and asphalt as well as scarce vegetation in urban areas lead to higher temperatures, study shows”

    “Exposure to deadly urban heat has tripled since the 1980s, and now affects nearly a quarter of the world’s population, a study has found.

    Scientists put the worrying trend down to the combination of rising temperatures and growing numbers of people living in urban areas, and warned of its potentially fatal impact.

    In recent decades, hundreds of millions of people have moved from rural areas to cities, which are now home to more than half the world’s population. Amid surfaces such as concrete and asphalt, which trap and concentrate heat, and little vegetation, temperatures are generally higher in urban areas.

    “This has broad effects,” said Cascade Tuholske, the lead author of the study published in the journal PNAS and a postdoctoral researcher at Columbia University’s Earth Institute. “It increases morbidity and mortality. It impacts people’s ability to work, and results in lower economic output. It exacerbates pre-existing health conditions.”

    The study used infrared satellite imagery and maximum daily heat and humidity readings from more than 13,000 cities from 1983 to 2016 to determine the number of people exposed to the days a year that exceeded 30C (86F) on the wet-bulb globe temperature scale (which takes into account the multiplier effect of high humidity) in an area. They matched the findings with the cities’ populations over the same period.

    The study found that the number of person-days (the cumulative population exposed to cumulative heat in a given year for a particular place) soared from 40bn a year in 1983 to 119bn in 2016, representing a threefold increase. In 2016, 1.7 billion people were subjected to extreme heat conditions on multiple days.

    Although it varied between cities and regions, scientists attributed two-thirds of the overall rise in exposure to increased urban populations and a third of it to global heating.

    The worst affected city was Dhaka. Between 1983 and 2016, during which time the city’s population rose dramatically, Bangladesh’s capital experienced an increase of 575 million person-days of extreme heat. Other cities that underwent rapid population growth include Shanghai and Guangzhou in China, Yangon in Myanmar, Bangkok in Thailand and Dubai in the United Arab Emirates.”

    It won’t stop them saying that it’s climate change wot dun it, though.


  16. Mark, So further urbanisation occurs in previously hot cities. More people means cities expand. Larger cities mean heat island effect increases and cities become ever more warm. Gosh more people affected by hotter city temperatures. Run for the hills, it’s massive climate change !!


  17. Alan, yes it’s true. The BBC confirms that flooding in cities is down to things like lack of soakaway, but it’s still all the fault of climate change:

    “Extreme weather: What causes flash flooding?”

    “Flash flooding affects cities across the world and has become more common because of climate change.”

    “Urban areas are more likely to experience this type of “surface water” flooding because they have a lot of hard surfaces – everything from paved front gardens to roads, car parks and high streets.

    When rain hits them it can’t soak into the ground as it would do in the countryside.”


    “In many places – including much of the UK – old sewer systems were built based on historic rainfall projections.

    Dr Veronica Edmonds-Brown of the University of Hertfordshire said the growth of London was also a problem as its Victorian era drainage system “cannot cope with the huge increase in population”.”

    But, inevitably:

    “Many factors contribute to flooding, but climate change makes extreme rainfall more likely.

    A warmer atmosphere can hold more moisture and so these storms become more intense.”


  18. Mark, not having any aptitude for meteorology, other than reading (and sometimes misreading) a weather app, I sometimes speculate and ponder the sentence you ended your 8.12 pm Oct 5th post with: “ A warmer atmosphere can hold more moisture and so these storms become more intense.” This phenomenon occurs leeward of mountain chains when a descending and warming wind (a chinook in Western Canada) is also be an intensely drying wind.

    In Calgary we enjoyed the warmth of a Chinook in the dead of winter as a respite from weeks of intense cold, but rushed out to protect our gardens’ snow cover which the chinook removed at an astonishing rate, visibly melting away before your eyes. If the snow were not preserved, then the garden would suffer later damage from the returning cold having lost its blanket of protective snow.

    So, if If the first part is of the claim is true then a mass of warmer air should be able to keep hold on to more water than a cool air mass. By this reasoning less water ought to be released from cooling warmer air. But of course raindrops are created as warm humid air is raised and cooled (some as ice crystals that melt on their descent). But surely with a warmer lower atmosphere, more of those raindrops will evaporate and less rain will fall. I have observed at many places where rain-laden clouds release rain but this never reaches the ground to the despair of farmers.

    Finally if the sentence were true, then more rain should fall in warmer months and during the day (compared to cooler nights). I have seen no data suggesting this.

    I don’t believe it.⚡️😢😂🥲😭😢😰😓😱. Or I need a bona fide meteorologist to explain it to me.


  19. Alan, like you, I just don’t know. I think it would be nice, however, if the claims were explained in great detail rather than baldly stated as something we had to accept because someone worried about climate change had stated it authoritatively.

    Personally, I’m confident the UHI is real, and is doing far more to turn cities into hot hell-holes than climate change is doing. I also think that inadequate drainage (compounded by a failure of authorities to keep the drains clean – many are already blocked by leaves here in Cockermouth, as they are every autumn) and huge areas of concreted over land denying soakaways between them are doing far more to create flooding than climate change is doing.

    However, climate change is great for those in charge – a get out of jail free card. It’s not bad planning laws allowing people to build on flood plains; it’s not inadequate drainage; it’s not blocked gulleys and culverts; it’s not too much concrete and not enough soakaway. No, climate change is to blame. Simples. And that way the local authority walks away from the mess they’ve made, and it’s not their fault. How could you say it is? What are you – some sort of denier or something?


  20. Dear Mark Hodgson, please stop supplying journalists with titles or a while.

    You post too much. I like a lot of what you post but you post too often and you include unnecessarily long quotes from articles that have caught your attention.

    Sorry to be so nasty so close to Christmas.

    Happy New Year!


  21. Vinny: I don’t see it like that. I see Mark as a voluble, irenic, wiki-maker.

    All three are positive but especially the last two.

    I’d need to explain the final term. Another time.

    Liked by 1 person

  22. Dear Mark,

    I am sorry about my comment last night. It was unfair and unpleasant to blame my short attention span on you.

    As you were.

    Liked by 2 people

  23. Vinny, thank you for that.

    My silence since your first comment wasn’t because I was sulking, by the way, just that I’ve been busy all day today and haven’t been near the internet until now.

    I understand that my extensive adding of links and extensive quotes from articles isn’t to everyone’s taste, so there was no need for you to apologise, though it was good of you to do so. Richard is correct that I basically use this website as a sort of mini-wiki, storing information about the climate alarmist net zero rubbish generated in the MSM, with a view to there being a record of it stored either on open mic or against whichever article might be relevant to it. I also seek to make it more widely available to those who might be interested, though I understand that not everybody will be. I recognise that I have a fault in cutting and pasting extensive sections from news articles, and I will endeavour to shorten them.

    Happy New Year to you too.


  24. “Lightning in India: A bolt from the blue that kills thousands”

    It’s climate change, of course:

    “…But the number of strikes have also risen sharply. India recorded more than 18 million lightning strikes between April 2020 and March 2021, according to a study by the non-profit Climate Resilient Observing Systems Promotion Council. This was a 34% rise over a similar period during the previous year. Satellite data gathered by the Indian Institute of Tropical Meteorology also shows strikes had “increased rapidly” between 1995 and 2014….

    …”Scientists say the threat from climate change is leading to increased lightning activity. Rising land and sea surface temperatures warm the air above and make more energy available to drive thunderstorms from where lightning emanates.

    A study by scientists at the University of California, Berkeley, said that lightning strikes in the US could increase by 12% for every degree rise in average temperature….”.

    But this is the clincher:

    “In India, increasing urbanisation and loss of tree cover have led to rise in temperatures.”

    The obsession with CO2 and other greenhouse gases leads to ignoring the other massive problems humankind is causing our environment in other ways, such as mass urbanisation, deforestation, etc.

    The article also nods to the importance of adaptation:

    “…So villagers have helped raise awareness and cut lightning deaths here by making cheap, homegrown lightning conductors to direct the electrical charge to the earth…The campaign has cut lightning deaths by 60% in some states….”.


  25. This article isn’t about UHI – rather it’s about the pollution problems associated with African and Asian mega-cities:

    “Satellite imagery shows air pollution rise in tropical ‘megacities’
    A new study uses satellites to measure pollution in African and Asian cities where there is little on-the-ground data collection”

    When it comes to messing with climate and air quality, I am pretty confident that huge urban sprawl and human activity associated with mega-cities are a significant part of the problem.

    “Air pollution has got far worse in 46 future megacities in tropical Africa, Asia and the Middle East, the study reveals. The deterioration in air quality has led to 180,000 extra deaths a year due to the combination of city expansion and worsening air pollution between 2005 and 2018.

    Agricultural burning from the areas around the cities is one of the main causes. But the deterioration is driven mostly by new sources such as fertiliser use in nearby farms and increased transport and industry. Problems with waste burning, including the burning of plastics, are widespread too. Cities in India are also being affected by new coal power stations that are being built in the country.”

    New coal power stations, eh? COP 26 was SUCH a success.


  26. “As urban temperatures climb, here’s what the modern city should look like
    Bob Ward
    Buildings, materials, habits: everything will have to change because of the climate emergency”

    It’s the usual sort of stuff from Bob Ward, but it does contain an interesting paragraph or two, which come close to being an admission, in my opinion, that UHI is huge (and therefore, in my estimation, not adequately provided for by adjustments to urban temperature gauges):

    “Cities are particularly at risk during heatwaves because of the urban heat island effect. The dark-coloured, human-made surfaces of buildings and roads tend to absorb sunlight and trap heat. As a result, the temperature of urban areas is often several degrees higher than the surrounding countryside. The very fabric of our urban areas makes them prone to overheating….

    …And of course, air conditioning units simply transfer heat from inside buildings into the surrounding area, making the outdoors even hotter….”


  27. This contains nothing new, and the BBC has taken the opportunity offered by a few days of very hot weather in some parts of the UK to trot this out as a general piece, though it’s really about the UHI. I love the picture adorning it, of people sitting outside their terraced house lapping up the sun, which rather goes against the BBC’s messaging. They’re certainly not sitting outside in the sun because their house is too hot.

    “Climate change: Heat deaths could triple by 2050”


  28. “Urban heat island intensity in London: An investigation of the impact of physical characteristics on changes in outdoor air temperature during summer”

    Almost 14 years old, but it has just come to my attention:

    “…The climatic variations in summer are controlled by classifying the data into clear sky, partially cloudy and cloudy periods. Geographical variation is controlled by classifying the data into core, urban and semi urban areas. Maximum daytime UHI of 8.9 °C is found in semi-urban area during partially cloudy period while maximum nocturnal UHI of 8.6 °C is found in urban area during clear sky period when the wind velocity is below 5 m/s. …”.


  29. “UK also broke its land surface temperature record”

    “The UK not only smashed its weather temperature record this week, it also set a new mark for surface heat.

    The 40.3C recorded at Coningsby, in Lincolnshire, was measured, as are all meteorological temperatures, in the shade and 1.5m (5ft) above the ground.

    But satellites are routinely mapping the energy retained in the “skin” of the Earth – what someone would feel if they placed their hand on the ground.

    And that rose to 48C on both Monday and Tuesday.

    Leading the way on the first day was Lakenheath, with 48.0C – on the second, Heathrow, topping out at 48.1C, with a couple of nearby London boroughs not far behind.”

    Yes, but, as the BBC does concede if you carry on reading:

    “Of course, both these locations have something in common – the wide expanse of asphalt and concrete you associate with an RAF base in the case of the Suffolk town and the big international airport just west of the capital.

    Construction materials are very good at absorbing and retaining heat compared with natural land cover.

    The previous record, of 44.7C, was set on 25 July 2019, in the Park Royal area of north-west London, which has a lot of those artificial structures expected of business and retail parks.”

    And if more evidence of the significant (and possibly not properly corrected for) impact of UHI is needed, how about this?

    “…The LST data also reveals something about the heat risk in different environments.

    There is much talk currently about the “urban heat-island effect” – the boost in warmth that city and town dwellers suffer because buildings and roads are so efficient at capturing the energy from the Sun.

    “And we saw that very clearly on Monday night in the difference between the cities and the rural background,” Dr Darren Ghent, a researcher with the National Centre for Earth Observation (NCEO) based at Leicester University, told BBC News.

    “In LST terms, the cities were at 25C to 27C, whereas the rural background was only in the high teens.

    That’s a difference of almost 10 degrees between the city and rural areas.

    “That’s real evidence of the urban heat island.””


  30. It appears that there is a motorway heat island effect to add to the urban heat island. Driving south down the M6 today, the temperatures recorded on the car thermometer rose steadily to 30C, which was no surprise.

    What did surprise me was the 3C drop in temperature within a couple of minutes of leaving the motorway. If motorway traffic and tarmac can distort temperature readings by 3C, goodness knows what is the level of distortion of temperatures at Heathrow and other airports and airfields. So much for the recent record temperatures in the UK which in reality may be no such thing.

    Liked by 1 person

  31. I can’t see why it would. In any event the motorway was busy and traffic was relatively slow-moving. I was probably driving at about the same speed when I left the motorway.


  32. “Climate change threatens health and survival of urban trees”

    This is an egregious example of conflating [man-made] climate change with the [very much man-made] urban heat island effect.


    Climate change threatens the health and survival of urban trees, with more than half of species already feeling the heat, according to a new study.

    City-dwelling oaks, maples, poplars, elms, pines and chestnuts are among more than 1,000 tree species flagged at risk due to climate change.

    Scientists want better protection of existing trees and for drought-resistant varieties to be planted.

    Trees have cooling effects and provide shade, making cities more liveable.

    Many trees in urban areas are already stressed because of climate change, and as it gets warmer and drier, the number of species at potential risk will increase, said Manuel Esperon-Rodriguez of Western Sydney University in Penrith, Australia….

    …Climate risk for species in urban areas is particularly high in cities in tropical regions, and in vulnerable countries such as India, Niger, Nigeria and Togo.

    In the UK, the researchers looked at five cities: Belfast, Birmingham, Bristol, London and York.

    They found that drier weather under climate change is expected to have a big impact on trees, particularly in York, London and Birmingham.

    The research is published in the journal, Nature Climate Change.

    No link to the study is provided. No sign of a climate disinformation specialist or a fact-checking team.


  33. I might add that even the chosen picture is in the form of propaganda – pollarded trees in winter in a UK city street (probably London). A casual viewer who didn’t know better might assume they weren’t doing very well, whereas in reality they are probably in fine fettle.

    Liked by 1 person

  34. As a former inhabitant of what is now Newham in east London (originally Manor Park) I confirm Mark’s belief that the much trimmed trees would have been in fine fettle. Every autumn the summer growth of new branches is removed down to the knobby ends of the main branches to create the monstrosities that the photograph shows. As to whether these plane trees are healthy, they were deliberately chosen as being a species that resisted pollution, and believe me before legislation controlling pollution from vehicles and coal fires those trees had much to contend with. As to drought resistance, plane trees have very deep roots.

    Liked by 2 people

  35. “Urban greening can reduce impact of global heating in cities, finds study
    Planting trees, rainwater gardens and de-paving can mitigate effects of climate crisis, according to analysis of 2,000 cities”

    Urban greening initiatives such as planting street trees, rainwater gardens and de-paving can help mitigate the impacts of urban heating due to the climate crisis and urban expansion, according to a study that has found cities have been warming by 0.5C a decade on average.

    Scientists at Nanjing and Yale Universities analysed satellite data from across 2,000 cities and compared surface temperature readings between cities and rural areas from 2002 to 2021.

    The study found on average that cities are warming by a rate of 0.56C a decade during the day and 0.43C a decade at night. In comparison, rural areas are warming by 0.4C a decade during the day and 0.37C a decade at night, which means urban areas are on average warming 29% more quickly than rural areas.

    The scientists found a link between a city’s size and the rate of urban warming, with megacities warming on average by 0.69C a decade during the day, compared with 0.41C a decade during the day in smaller cities….

    …In about 90% of the cities surveyed, scientists found the climate crisis is the greatest contributor to urban warming, with about 0.3C of heating a decade attributed to human-induced climate change on average. However, scientists noted that urban expansion can also influence urban heating – in parts of China and India, rapid urbanisation is contributing to about 0.23C of urban warming a decade….

    That last paragraph is very important, I think.


  36. “U.S. Warming Over Last 50 Years Exaggerated by Up to 50%, New Evidence Shows”

    The widespread use of regularly adjusted global and local surface temperature datasets showing increasingly implausible rates of warming has been dealt a further blow with new groundbreaking research that shows 50% less warming over 50 years across the eastern United States. The research attempts to remove distortions caused by increasing urban heat and uses human-made structure density data over 50 years supplied by the Landsat satellites. The 50% reduction in the warming trend is by comparison with the official National Oceanic and Atmospheric Administration (NOAA) homogenised surface temperature dataset.

    The research was compiled by two atmospheric scientists at the University of Alabama in Huntsville, Dr. Roy Spencer and Professor John Christy. They used a dataset of urbanisation changes called ‘Built-Up’ to determine the average effect that urbanisation has had on surface temperatures. Urbanisation differences were compared to temperature differences from closely spaced weather stations. The temperature plotted was in the morning during the summertime. A full methodology of the project is shown here in a posting on Dr. Spencer’s blog.

    Dr. Spencer believes that the ‘Built-Up’ dataset, which extends back to the 1970s, will be useful in ‘de-urbanising’ land-based surface temperature measurements in the U.S. as well as other countries….


  37. ps – notice London area seems to always have the highest temps on the weather maps, wonder why?


  38. “Summer Temperatures in Canada Have Been Massively Exaggerated Since 1978”

    Further holes have been blown in the regularly adjusted global and local surface databases that show increasingly implausible rates of warming. The latest work from Messrs Roy Spencer and John Christy reveals that since 1978 about half of the summer night-time warming across 10 mostly metro areas of Canada was due to increased urbanisation. This urban heat effect accounted for 20% of the day-time warming produced by ‘homogenised’ temperature datasets. The two atmospheric scientists recently published similar results showing 50% less warming over 50 years across the eastern United States….

    …It is notable that Calgary, Ottawa, Windsor, Montreal and Edmonton are the five station locations with the greatest rate of increased urbanisation since the 1970s as measured by Landsat, and therefore the highest rate of spurious warming. Over the 10 highest growth locations shown, “48% of the average warming trend is estimated to be due to urbanisation alone”.

    For the 10 most increasingly urbanised stations, the average reduction in the observed afternoon warming trend is 20%. The scientists note, as do many others, that the urban heat effect on temperatures is larger detectable at night when solar energy absorbed by heat-retaining building material is slowly released.

    This work is part of an ongoing investigation by Spencer and Christy into the degree to which surface temperature datasets are producing warming trends that have been exaggerated by increased urbanisation. Preliminary analysis has also been done for the U.K., France, Australia and China. It seems the more work they do, the more critical they become of the surface datasets. Current ‘homogenisation’ techniques for thermometer data adjustments do not explicitly attempt to correct urban trends to match rural ones, they point out. Instead, it appears the reverse occurs. The work of the U.S. meteorologist Anthony Watts is referenced. He found that the U.S. homogenised dataset produced temperature trends “as large as those produced by the stations with the worst siting in terms of spurious heat sources”.

    The scientists also refer to a rarely-publicised dataset compiled by the U.S. weather service NOAA from 114 nationwide stations designed to provide recordings away from urban heat distortions. The measurements started in 2005, and to date show little if any warming across the U.S….


  39. More from the Daily Sceptic in similar vein to the article I linked to in my last comment on this thread:

    “Two Top Climate Scientists Find Further Evidence That Global Warming Has Been Exaggerated”

    …In their ground-breaking work, Spencer and Christy use a satellite dataset of urbanisation called ‘Built Up’ to determine the average effect that urbanisation has had on surface temperatures. Urbanisation differences were compared to temperature changes from closely-spaced weather stations. Earlier findings suggested that in the last 50 years, there was a remarkable 50% less warming across the eastern United States. Again the work is preliminary and the scientists suggest it is likely to be at the upper limit of de-urbanisation adjustments. Nevertheless, there were many surprises, not least in data from airports. These places contribute many readings to global datasets, but massive distortions were found. One of the worst examples was Orlando International Airport where the warming was measured at 0.3°C per decade. This fell to a de-urbanised figure of just 0.07°C…


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