Tag Archives: Urban heat islands

New York City's summers may heat up

EMBARGOED until 2301 GMT on Tuesday 21 May
Cities are liable to heat up much more than open countryside as the climate warms – and in the case of New York City, this could mean a big increase in heat-related deaths.

LONDON, 22 May – If you are a New Yorker, global warming could seriously damage your health. The sweltering summer temperatures of the Big Apple are likely to go on rising through the next six decades, and deaths from heatstroke and other forms of hyperthermia could increase.

Scientists from Columbia University report in Nature Climate Change that temperature-related deaths in Manhattan, at the heart of New York, could increase by 20% during the 2020s, and by as much as 90% by the 2080s.

Cities are always conspicuously warmer than the surrounding countryside – meteorologists call this the “heat island effect” – and can become lethal zones during protracted heat waves.

In 1995, an estimated 700 people died prematurely in one baking summer in Chicago. In 2010, a heat wave in Russia is thought to have claimed 55,000 lives. In 2003, in central and western Europe, an estimated 70,000 died prematurely in a summer of unprecedented temperatures.

New York is a city of extremes of heat and cold. During the 20th century, average temperatures increased by 2°C, far faster than the increase for the nation or the globe as a whole.

In each of the past three years, summer temperatures have pushed the thermometer to beyond 38°C – normal body temperature or higher – and 2012 was the city’s warmest year on record.

Tiantian Li, of the Chinese Centre for Disease Control and Prevention in Beijing, who did his research while at Columbia, and Patrick Kinney and Radley Horton took as their baseline the 1980s, when slightly more Manhattanites were estimated to have died from heat than from cold, and began to look at projections for the future.

They took temperature projections from 16 climate models, scaled them to Manhattan, and tested them under two scenarios; one that assumed rapid growth and few limits to carbon dioxide emissions; and another that allowed for slower growth and a decrease in emissions by 2040.

Hot period lengthens

 

In all 32 projections, temperature-related deaths increased, and increased steeply with time. Because winter temperatures would be higher, there would be fewer deaths from cold, but these were more than offset by projected deaths from the big heat to come.

In the worst-case scenario, even if Manhattan’s current population of 1.6 million remained the same, an estimated 1,000 lives a year would be claimed by heat waves.

The largest percentage increases would not be in the traditionally baking months of high summer, the researchers found, but in May and September – periods now considered pleasant and equable, but likely under global warming to be enfolded into the long hot summer.

Research such as this is a projection of what could happen, not what will. The scientists did not take into account possible adaptations to urban warming – greater investment in air conditioning, for instance, or the establishment of systems of heat alerts and cooling shelters.

People too, might perhaps physiologically adapt to cope better with sweltering summers. But the authors also point out that their projections may be under-estimates.

“Our method may give conservative projections of future mortality effects as the population of NYC is expected to rise and age for several decades,” they warn.

“Changes in other factors that influence population vulnerability, such as general health, access to health care, socio-economic status and exposure to public health messaging are more uncertain.” – Climate News Network

EMBARGOED until 2301 GMT on Tuesday 21 May
Cities are liable to heat up much more than open countryside as the climate warms – and in the case of New York City, this could mean a big increase in heat-related deaths.

LONDON, 22 May – If you are a New Yorker, global warming could seriously damage your health. The sweltering summer temperatures of the Big Apple are likely to go on rising through the next six decades, and deaths from heatstroke and other forms of hyperthermia could increase.

Scientists from Columbia University report in Nature Climate Change that temperature-related deaths in Manhattan, at the heart of New York, could increase by 20% during the 2020s, and by as much as 90% by the 2080s.

Cities are always conspicuously warmer than the surrounding countryside – meteorologists call this the “heat island effect” – and can become lethal zones during protracted heat waves.

In 1995, an estimated 700 people died prematurely in one baking summer in Chicago. In 2010, a heat wave in Russia is thought to have claimed 55,000 lives. In 2003, in central and western Europe, an estimated 70,000 died prematurely in a summer of unprecedented temperatures.

New York is a city of extremes of heat and cold. During the 20th century, average temperatures increased by 2°C, far faster than the increase for the nation or the globe as a whole.

In each of the past three years, summer temperatures have pushed the thermometer to beyond 38°C – normal body temperature or higher – and 2012 was the city’s warmest year on record.

Tiantian Li, of the Chinese Centre for Disease Control and Prevention in Beijing, who did his research while at Columbia, and Patrick Kinney and Radley Horton took as their baseline the 1980s, when slightly more Manhattanites were estimated to have died from heat than from cold, and began to look at projections for the future.

They took temperature projections from 16 climate models, scaled them to Manhattan, and tested them under two scenarios; one that assumed rapid growth and few limits to carbon dioxide emissions; and another that allowed for slower growth and a decrease in emissions by 2040.

Hot period lengthens

 

In all 32 projections, temperature-related deaths increased, and increased steeply with time. Because winter temperatures would be higher, there would be fewer deaths from cold, but these were more than offset by projected deaths from the big heat to come.

In the worst-case scenario, even if Manhattan’s current population of 1.6 million remained the same, an estimated 1,000 lives a year would be claimed by heat waves.

The largest percentage increases would not be in the traditionally baking months of high summer, the researchers found, but in May and September – periods now considered pleasant and equable, but likely under global warming to be enfolded into the long hot summer.

Research such as this is a projection of what could happen, not what will. The scientists did not take into account possible adaptations to urban warming – greater investment in air conditioning, for instance, or the establishment of systems of heat alerts and cooling shelters.

People too, might perhaps physiologically adapt to cope better with sweltering summers. But the authors also point out that their projections may be under-estimates.

“Our method may give conservative projections of future mortality effects as the population of NYC is expected to rise and age for several decades,” they warn.

“Changes in other factors that influence population vulnerability, such as general health, access to health care, socio-economic status and exposure to public health messaging are more uncertain.” – Climate News Network

New York City’s summers may heat up

EMBARGOED until 2301 GMT on Tuesday 21 May Cities are liable to heat up much more than open countryside as the climate warms – and in the case of New York City, this could mean a big increase in heat-related deaths. LONDON, 22 May – If you are a New Yorker, global warming could seriously damage your health. The sweltering summer temperatures of the Big Apple are likely to go on rising through the next six decades, and deaths from heatstroke and other forms of hyperthermia could increase. Scientists from Columbia University report in Nature Climate Change that temperature-related deaths in Manhattan, at the heart of New York, could increase by 20% during the 2020s, and by as much as 90% by the 2080s. Cities are always conspicuously warmer than the surrounding countryside – meteorologists call this the “heat island effect” – and can become lethal zones during protracted heat waves. In 1995, an estimated 700 people died prematurely in one baking summer in Chicago. In 2010, a heat wave in Russia is thought to have claimed 55,000 lives. In 2003, in central and western Europe, an estimated 70,000 died prematurely in a summer of unprecedented temperatures. New York is a city of extremes of heat and cold. During the 20th century, average temperatures increased by 2°C, far faster than the increase for the nation or the globe as a whole. In each of the past three years, summer temperatures have pushed the thermometer to beyond 38°C – normal body temperature or higher – and 2012 was the city’s warmest year on record. Tiantian Li, of the Chinese Centre for Disease Control and Prevention in Beijing, who did his research while at Columbia, and Patrick Kinney and Radley Horton took as their baseline the 1980s, when slightly more Manhattanites were estimated to have died from heat than from cold, and began to look at projections for the future. They took temperature projections from 16 climate models, scaled them to Manhattan, and tested them under two scenarios; one that assumed rapid growth and few limits to carbon dioxide emissions; and another that allowed for slower growth and a decrease in emissions by 2040.

Hot period lengthens

  In all 32 projections, temperature-related deaths increased, and increased steeply with time. Because winter temperatures would be higher, there would be fewer deaths from cold, but these were more than offset by projected deaths from the big heat to come. In the worst-case scenario, even if Manhattan’s current population of 1.6 million remained the same, an estimated 1,000 lives a year would be claimed by heat waves. The largest percentage increases would not be in the traditionally baking months of high summer, the researchers found, but in May and September – periods now considered pleasant and equable, but likely under global warming to be enfolded into the long hot summer. Research such as this is a projection of what could happen, not what will. The scientists did not take into account possible adaptations to urban warming – greater investment in air conditioning, for instance, or the establishment of systems of heat alerts and cooling shelters. People too, might perhaps physiologically adapt to cope better with sweltering summers. But the authors also point out that their projections may be under-estimates. “Our method may give conservative projections of future mortality effects as the population of NYC is expected to rise and age for several decades,” they warn. “Changes in other factors that influence population vulnerability, such as general health, access to health care, socio-economic status and exposure to public health messaging are more uncertain.” – Climate News Network

EMBARGOED until 2301 GMT on Tuesday 21 May Cities are liable to heat up much more than open countryside as the climate warms – and in the case of New York City, this could mean a big increase in heat-related deaths. LONDON, 22 May – If you are a New Yorker, global warming could seriously damage your health. The sweltering summer temperatures of the Big Apple are likely to go on rising through the next six decades, and deaths from heatstroke and other forms of hyperthermia could increase. Scientists from Columbia University report in Nature Climate Change that temperature-related deaths in Manhattan, at the heart of New York, could increase by 20% during the 2020s, and by as much as 90% by the 2080s. Cities are always conspicuously warmer than the surrounding countryside – meteorologists call this the “heat island effect” – and can become lethal zones during protracted heat waves. In 1995, an estimated 700 people died prematurely in one baking summer in Chicago. In 2010, a heat wave in Russia is thought to have claimed 55,000 lives. In 2003, in central and western Europe, an estimated 70,000 died prematurely in a summer of unprecedented temperatures. New York is a city of extremes of heat and cold. During the 20th century, average temperatures increased by 2°C, far faster than the increase for the nation or the globe as a whole. In each of the past three years, summer temperatures have pushed the thermometer to beyond 38°C – normal body temperature or higher – and 2012 was the city’s warmest year on record. Tiantian Li, of the Chinese Centre for Disease Control and Prevention in Beijing, who did his research while at Columbia, and Patrick Kinney and Radley Horton took as their baseline the 1980s, when slightly more Manhattanites were estimated to have died from heat than from cold, and began to look at projections for the future. They took temperature projections from 16 climate models, scaled them to Manhattan, and tested them under two scenarios; one that assumed rapid growth and few limits to carbon dioxide emissions; and another that allowed for slower growth and a decrease in emissions by 2040.

Hot period lengthens

  In all 32 projections, temperature-related deaths increased, and increased steeply with time. Because winter temperatures would be higher, there would be fewer deaths from cold, but these were more than offset by projected deaths from the big heat to come. In the worst-case scenario, even if Manhattan’s current population of 1.6 million remained the same, an estimated 1,000 lives a year would be claimed by heat waves. The largest percentage increases would not be in the traditionally baking months of high summer, the researchers found, but in May and September – periods now considered pleasant and equable, but likely under global warming to be enfolded into the long hot summer. Research such as this is a projection of what could happen, not what will. The scientists did not take into account possible adaptations to urban warming – greater investment in air conditioning, for instance, or the establishment of systems of heat alerts and cooling shelters. People too, might perhaps physiologically adapt to cope better with sweltering summers. But the authors also point out that their projections may be under-estimates. “Our method may give conservative projections of future mortality effects as the population of NYC is expected to rise and age for several decades,” they warn. “Changes in other factors that influence population vulnerability, such as general health, access to health care, socio-economic status and exposure to public health messaging are more uncertain.” – Climate News Network

Cut your carbon: Stay warm, lose the lawn

FOR IMMEDIATE RELEASE Researchers may have found the way to a more comfortable life for suburbanites: garden lawns are more prolific carbon emitters than some farm crops, and keeping yourself warm uses much more energy than running an air conditioner. LONDON, 27 April – Here is some very limited advice on how to reduce your carbon footprint in suburban America: if you have a lawn, dig it up and plant a crop of maize. And if you live in Minneapolis, sell up and move to Miami. Two research papers in two journals have looked at two of those either/or questions that keep academics busy and dinner parties animated. Researchers at Elizabethtown College in Lancaster County, Pennsylvania, decided to look at what happens when farmland is converted to urban property. So for 10 weeks in the autumn of 2011, they visited and sampled the carbon dioxide release, soil moisture and temperatures, from urban lawns and from fields of corn, known also as Zea mays. They report in the Soil Science Society of America Journal that freshly mown grass sward won the dubious trophy for high greenhouse achievement. That is because lawns, on average, were hotter. “As you increase temperature, you increase biological activity – be it microbial, plant, fungal or animal”, said David Bowne, a biologist at the college. More biological activity meant more respiration, and more carbon dioxide releases. The higher lawn temperatures seem to be part of the urban heat island effect. Cities, notoriously, are much warmer than the surrounding countryside: roofs, roads, pavements and parking lots are dark, and absorb more sunlight, raising the ambient atmospheric temperatures overall. What the researchers had not quite expected, however, was to observe the effect on such a local scale. The research team found that urban development just 175 metres from a test location can cause an increase in temperature. The research is a small part of a much larger, global effort to understand what changes in land use do to climate.

Warmth is costly

  “If we go from one land use to another land use, how does that impact carbon cycling which in turn can affect climate change? Our study touches on one component of that cycle, and more research is needed to address this huge topic”, said Dr Bowne. Meanwhile, over at the University of Michigan, Ann Arbor, Michael Sivak asked himself the question: which demands more energy, air conditioning or central heating? He reports in Environmental Research Letters that he compared the costs of climate control in America’s warmest large city, and its coldest: Miami and Minneapolis respectively. The question isn’t an easy one: both air-conditioning and central heating systems use energy, but do they do so with comparable efficiency? One runs on electricity, the other sometimes on natural gas or oil. Even in Miami, people occasionally need to turn up the thermostat. Minneapolis, like any mid-Western city, can become uncomfortably hot, so both cities use both forms of climate control. The answer however proved to be quite straightforward.  Professor Sivak concludes that the cost of staying comfortably warm in Minneapolis requires 3.5 times the energy needed to stay cool in Miami. Miami’s advantage might be even greater, if only because humans tend to tolerate heat rather more good-temperedly than cold. “The traditional discussion of climatology and energy demand concentrates on the energy demands for cooling in hot climates,” Sivak writes. “However, the present results indicate that the focus should be paid to the opposite end of the scale as well.”- Climate News Network

FOR IMMEDIATE RELEASE Researchers may have found the way to a more comfortable life for suburbanites: garden lawns are more prolific carbon emitters than some farm crops, and keeping yourself warm uses much more energy than running an air conditioner. LONDON, 27 April – Here is some very limited advice on how to reduce your carbon footprint in suburban America: if you have a lawn, dig it up and plant a crop of maize. And if you live in Minneapolis, sell up and move to Miami. Two research papers in two journals have looked at two of those either/or questions that keep academics busy and dinner parties animated. Researchers at Elizabethtown College in Lancaster County, Pennsylvania, decided to look at what happens when farmland is converted to urban property. So for 10 weeks in the autumn of 2011, they visited and sampled the carbon dioxide release, soil moisture and temperatures, from urban lawns and from fields of corn, known also as Zea mays. They report in the Soil Science Society of America Journal that freshly mown grass sward won the dubious trophy for high greenhouse achievement. That is because lawns, on average, were hotter. “As you increase temperature, you increase biological activity – be it microbial, plant, fungal or animal”, said David Bowne, a biologist at the college. More biological activity meant more respiration, and more carbon dioxide releases. The higher lawn temperatures seem to be part of the urban heat island effect. Cities, notoriously, are much warmer than the surrounding countryside: roofs, roads, pavements and parking lots are dark, and absorb more sunlight, raising the ambient atmospheric temperatures overall. What the researchers had not quite expected, however, was to observe the effect on such a local scale. The research team found that urban development just 175 metres from a test location can cause an increase in temperature. The research is a small part of a much larger, global effort to understand what changes in land use do to climate.

Warmth is costly

  “If we go from one land use to another land use, how does that impact carbon cycling which in turn can affect climate change? Our study touches on one component of that cycle, and more research is needed to address this huge topic”, said Dr Bowne. Meanwhile, over at the University of Michigan, Ann Arbor, Michael Sivak asked himself the question: which demands more energy, air conditioning or central heating? He reports in Environmental Research Letters that he compared the costs of climate control in America’s warmest large city, and its coldest: Miami and Minneapolis respectively. The question isn’t an easy one: both air-conditioning and central heating systems use energy, but do they do so with comparable efficiency? One runs on electricity, the other sometimes on natural gas or oil. Even in Miami, people occasionally need to turn up the thermostat. Minneapolis, like any mid-Western city, can become uncomfortably hot, so both cities use both forms of climate control. The answer however proved to be quite straightforward.  Professor Sivak concludes that the cost of staying comfortably warm in Minneapolis requires 3.5 times the energy needed to stay cool in Miami. Miami’s advantage might be even greater, if only because humans tend to tolerate heat rather more good-temperedly than cold. “The traditional discussion of climatology and energy demand concentrates on the energy demands for cooling in hot climates,” Sivak writes. “However, the present results indicate that the focus should be paid to the opposite end of the scale as well.”- Climate News Network

Climate curbs can be household killers

EMBARGOED until 0001 GMT on Monday 25 February Can you be too zealous in conserving warmth to limit climate change? Yes, say British researchers: their study has found that attempts to prevent heat leaking out of buildings can endanger health, and even life itself. LONDON, 25 February – Overheating in buildings caused by improved insulation and lack of proper ventilation is causing increased illness and deaths for the occupants of both old and new properties. New regulations in European countries designed to combat climate change by preventing heat loss from buildings has caused many homes to become dangerously hot, not just in summer months but all year round. Researchers fear that as attempts are made to design more homes that are zero-rated for carbon, more and more of them will become health risks to those who live in them, particularly the elderly and young children. The old and very young do not have the ability to regulate body temperature and can overheat and die. The NHBC Foundation, a UK building research group, says in a report that the worst-affected properties at the moment are small apartments and refurbished older buildings, where extra insulation means it is almost impossible to ventilate homes properly. This is particularly bad in urban areas, where people do not open windows at night from fear of noise, pollution or crime. It is also made worse by the heat island effect, where buildings are still hot at night and the air outside may be warmer than inside. In London, for example, the city temperature can be 9°C higher at night than the surrounding countryside. This pushes summer temperatures well over the danger limit for people over 65 and for very young children trying to sleep in the inner city. Opening windows would only make the situation worse by letting in even warmer air. The current regulations do not stipulate what constitutes health-threatening overheating, but the report says that danger begins if temperatures stay above 25°C for more than a few hours. The ability to sleep is affected if the temperature exceeds 24°C. The research took place in Britain and the report acknowledges that in some tropical countries people are adapted to warmer conditions. The authors report that even in Europe people do adapt over time, but suggest climate change may build heat waves faster than the population can tolerate.

Review needed

  Because of the slow response of the human body, a heat wave early in the summer is expected to kill more people, because they will not have had time to adapt. The report lists mild heat-related illnesses as dehydration, prickly heat, cramps, rashes, fainting, and at work the loss of productivity and concentration that can lead to accidents (see our story of 24 February: NY-on-the-Gulf: The warmer world of 2200). If people do not find ways of cooling down, then fatal heat stroke can be rapid. Obese people are at greater risk because they heat up faster and find it harder to cool down. The report notes that in a four-day heat wave in 1995 an extra 619 people died in England and Wales, and in August 2003, in a three-week European heat wave, 35,000 people died as a result. Although heat is not as big a killer as cold in the UK – 25,000 excess deaths in winter are due to cold and only 2,000 to summer heat – the researchers say heat deaths will increase. This is particularly because indoor heat deaths are not counted in these statistics, since most are put down to other causes like heart failure. The report says building regulations should be urgently reviewed so that an upper limit is placed on temperature in dwellings, with 25°C being the probable threshold. If the temperature is likely to exceed that – and it often will, because of increased insulation or lack of ventilation – then some means of cooling the homes needs to be included in the design. If it is not, the occupants will be at risk of illness and death. – Climate News Network

EMBARGOED until 0001 GMT on Monday 25 February Can you be too zealous in conserving warmth to limit climate change? Yes, say British researchers: their study has found that attempts to prevent heat leaking out of buildings can endanger health, and even life itself. LONDON, 25 February – Overheating in buildings caused by improved insulation and lack of proper ventilation is causing increased illness and deaths for the occupants of both old and new properties. New regulations in European countries designed to combat climate change by preventing heat loss from buildings has caused many homes to become dangerously hot, not just in summer months but all year round. Researchers fear that as attempts are made to design more homes that are zero-rated for carbon, more and more of them will become health risks to those who live in them, particularly the elderly and young children. The old and very young do not have the ability to regulate body temperature and can overheat and die. The NHBC Foundation, a UK building research group, says in a report that the worst-affected properties at the moment are small apartments and refurbished older buildings, where extra insulation means it is almost impossible to ventilate homes properly. This is particularly bad in urban areas, where people do not open windows at night from fear of noise, pollution or crime. It is also made worse by the heat island effect, where buildings are still hot at night and the air outside may be warmer than inside. In London, for example, the city temperature can be 9°C higher at night than the surrounding countryside. This pushes summer temperatures well over the danger limit for people over 65 and for very young children trying to sleep in the inner city. Opening windows would only make the situation worse by letting in even warmer air. The current regulations do not stipulate what constitutes health-threatening overheating, but the report says that danger begins if temperatures stay above 25°C for more than a few hours. The ability to sleep is affected if the temperature exceeds 24°C. The research took place in Britain and the report acknowledges that in some tropical countries people are adapted to warmer conditions. The authors report that even in Europe people do adapt over time, but suggest climate change may build heat waves faster than the population can tolerate.

Review needed

  Because of the slow response of the human body, a heat wave early in the summer is expected to kill more people, because they will not have had time to adapt. The report lists mild heat-related illnesses as dehydration, prickly heat, cramps, rashes, fainting, and at work the loss of productivity and concentration that can lead to accidents (see our story of 24 February: NY-on-the-Gulf: The warmer world of 2200). If people do not find ways of cooling down, then fatal heat stroke can be rapid. Obese people are at greater risk because they heat up faster and find it harder to cool down. The report notes that in a four-day heat wave in 1995 an extra 619 people died in England and Wales, and in August 2003, in a three-week European heat wave, 35,000 people died as a result. Although heat is not as big a killer as cold in the UK – 25,000 excess deaths in winter are due to cold and only 2,000 to summer heat – the researchers say heat deaths will increase. This is particularly because indoor heat deaths are not counted in these statistics, since most are put down to other causes like heart failure. The report says building regulations should be urgently reviewed so that an upper limit is placed on temperature in dwellings, with 25°C being the probable threshold. If the temperature is likely to exceed that – and it often will, because of increased insulation or lack of ventilation – then some means of cooling the homes needs to be included in the design. If it is not, the occupants will be at risk of illness and death. – Climate News Network

Urban heat has far-flung impact

EMBARGOED until 1800 GMT on Sunday 27 January Cities are affecting global climate patterns in ways unsuspected till now, say US researchers who think climatologists should factor energy consumption patterns into their models. LONDON, 27 January – Urban real estate is literally hot property – so hot that it can affect not just the countryside a thousand kilometres away, but even weather patterns over whole continents. A team from Scripps Institution of Oceanography in San Diego, Florida State University and the National Center for Atmospheric Research in Boulder, Colorado, report in Nature Climate Change that they looked at a phenomenon known as the urban heat island. Meteorologists have known for decades that cities can be up to 5°C warmer than the surrounding countryside, thanks to the greater densities of traffic, people, lighting, heating, air conditioning, factories and the thermal properties of tarmac and concrete. The world’s cities are growing: more than half of all humanity is now crowded into urban areas. Now it seems that urban waste heat could account for hitherto unexplained patterns of warming by 1°C in winter in northern America and northern Asia. At the same time, the air temperatures over Europe during the autumn can fall by as much as 1°C, because of the urban heat island effect. The overall effect on global average temperatures is negligible, but the regional effects can certainly be estimated. Effectively, fossil fuel is a form of stored sunshine: collected by plants over millions of years during the Carboniferous and released on a huge scale in the last 100 years or so. The carbon dioxide released is the prime cause of global warming, but the newly-liberated warmth of the Carboniferous, too, has an impact.

Atmospheric circulation altered

Guang Zhang of Scripps and colleagues considered the human energy consumption in 2006. Of this 16 trillion watts, they calculated that nearly 7 trillion was consumed in 86 metropolitan areas in the northern hemisphere. In Tokyo alone, in the early winter morning, the rate of consumption averaged almost 1,600 watts per square metre. They modelled the patterns of consumption by computer, and calculated that waste heat would be enough to widen the jet stream, that great circulatory system in the stratosphere, to move heat around and make some regions noticeably warmer, others cooler. “What we found is that energy use from multiple urban areas collectively can warm the atmosphere remotely, thousands of miles away from the energy consumption regions. This is accomplished through atmospheric circulation change,” said Zhang. The researchers argue that future simulations of climate change might need to include – along with greenhouse gas emissions, aerosol discharges and land use change – patterns of energy consumption as well. “A better and more accurate estimate of global energy use based on city-by-city information should be developed to fully account for the climate impact due to energy consumption in future climate change projections,” they conclude.  – Climate News Network

EMBARGOED until 1800 GMT on Sunday 27 January Cities are affecting global climate patterns in ways unsuspected till now, say US researchers who think climatologists should factor energy consumption patterns into their models. LONDON, 27 January – Urban real estate is literally hot property – so hot that it can affect not just the countryside a thousand kilometres away, but even weather patterns over whole continents. A team from Scripps Institution of Oceanography in San Diego, Florida State University and the National Center for Atmospheric Research in Boulder, Colorado, report in Nature Climate Change that they looked at a phenomenon known as the urban heat island. Meteorologists have known for decades that cities can be up to 5°C warmer than the surrounding countryside, thanks to the greater densities of traffic, people, lighting, heating, air conditioning, factories and the thermal properties of tarmac and concrete. The world’s cities are growing: more than half of all humanity is now crowded into urban areas. Now it seems that urban waste heat could account for hitherto unexplained patterns of warming by 1°C in winter in northern America and northern Asia. At the same time, the air temperatures over Europe during the autumn can fall by as much as 1°C, because of the urban heat island effect. The overall effect on global average temperatures is negligible, but the regional effects can certainly be estimated. Effectively, fossil fuel is a form of stored sunshine: collected by plants over millions of years during the Carboniferous and released on a huge scale in the last 100 years or so. The carbon dioxide released is the prime cause of global warming, but the newly-liberated warmth of the Carboniferous, too, has an impact.

Atmospheric circulation altered

Guang Zhang of Scripps and colleagues considered the human energy consumption in 2006. Of this 16 trillion watts, they calculated that nearly 7 trillion was consumed in 86 metropolitan areas in the northern hemisphere. In Tokyo alone, in the early winter morning, the rate of consumption averaged almost 1,600 watts per square metre. They modelled the patterns of consumption by computer, and calculated that waste heat would be enough to widen the jet stream, that great circulatory system in the stratosphere, to move heat around and make some regions noticeably warmer, others cooler. “What we found is that energy use from multiple urban areas collectively can warm the atmosphere remotely, thousands of miles away from the energy consumption regions. This is accomplished through atmospheric circulation change,” said Zhang. The researchers argue that future simulations of climate change might need to include – along with greenhouse gas emissions, aerosol discharges and land use change – patterns of energy consumption as well. “A better and more accurate estimate of global energy use based on city-by-city information should be developed to fully account for the climate impact due to energy consumption in future climate change projections,” they conclude.  – Climate News Network