Hot days cooled by growth in grasslands

March 14, 2013
Hot days cooled by growth in grasslands

Our changing use of the land may have been taking the edge off hot days, scientists say.

The study, published in Geophysical Research Letters, suggests that the global pattern of replacing trees with grasslands could have been affecting .

'We find that replacing tree cover with grasslands leads to a weak cooling effect, in the opposite direction of climate change caused by like carbon dioxide,' says Dr Nikos Christidis from the Met Office, who led the study.

The team used a to look at historical changes in land use, for the first time examining their effect on the climate in the context of other climate influences.

'Over the last century there have been significant changes in land use,' he explains. 'The main one has been the replacement of trees with grasslands.'

'When you replace trees with grasslands, the surface becomes more reflective.'

'This means that, on hot days, when there is normally lots of sunlight, more heat is reflected back off the surface, leading to a small cooling effect.'

'There are also changes in the due to alterations in the water cycle, as well as changes in or uptake. These are more complicated and can lead to opposite effects in different regions.'

In some parts of the tropics, for example, changes in the water cycle dominate and may make hot days even hotter.

Extreme heat can be a killer. In August 2003, a heat wave that affected large parts of Western Europe led to 2,000 more UK deaths than usual for the time of year.

Christidis warns that any cooling effect created by a growth in grasslands is likely to be far outstripped by warming from greenhouse gases.

'In the 50s and 60s, this was probably taking the edge off extreme hot days but, as time goes by, the effect is being overwhelmed by warming from ,' he says.

Christidis hopes that this work will inspire better representations of the effect of land use change in climate models, ultimately improving predictions of climate change.

Explore further: CO2 effects on plants increases global warming

More information: Christidis, N. et al. The role of land use change in the recent warming of daily extreme temperatures, Geophysical Research Letters, 2013, DOI: 10.1002/grl.50159

Related Stories

CO2 effects on plants increases global warming

May 3, 2010

Trees and other plants help keep the planet cool, but rising levels of carbon dioxide in the atmosphere are turning down this global air conditioner. According to a new study by researchers at the Carnegie Institution for ...

Water evaporated from trees cools global climate

September 14, 2011

Scientists have long debated about the impact on global climate of water evaporated from vegetation. New research from Carnegie's Global Ecology department concludes that evaporated water helps cool the earth as a whole, ...

Land conversion and climate threaten land birds

June 5, 2007

Land conversion and climate change have already had significant impacts on biodiversity and associated ecosystem services.Using future land-cover projections from the recently completed Millennium Ecosystem Assessment, Walter ...

Stabilizing climate requires near-zero carbon emissions

February 15, 2008

Now that scientists have reached a consensus that carbon dioxide emissions from human activities are the major cause of global warming, the next question is: How can we stop it" Can we just cut back on carbon, or do we need ...

The forest paradox during heatwaves

September 6, 2010

Comparatively speaking, forests initially have a weaker cooling effect during heatwaves than open grassland. This is revealed in a study that could help refine models for weather and climate forecasts. Moreover, it also provides ...

Recommended for you

Cool roofs have water saving benefits too

October 20, 2017

The energy and climate benefits of cool roofs have been well established: By reflecting rather than absorbing the sun's energy, light-colored roofs keep buildings, cities, and even the entire planet cooler. Now a new study ...

Carbon coating gives biochar its garden-greening power

October 20, 2017

For more than 100 years, biochar, a carbon-rich, charcoal-like substance made from oxygen-deprived plant or other organic matter, has both delighted and puzzled scientists. As a soil additive, biochar can store carbon and ...

Study finds pollution is deadlier than war, disaster, hunger

October 20, 2017

Environmental pollution—from filthy air to contaminated water—is killing more people every year than all war and violence in the world. More than smoking, hunger or natural disasters. More than AIDS, tuberculosis and ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.