Faster Climate Change Predicted as Air Quality Improves

June 29, 2005

Global warming may proceed faster and be more severe than previously predicted according to research about to be published in the scientific journal Nature. Reductions in airborne particle pollution, or aerosols, as air quality is improved, will amplify climate change by reducing the cooling effect due to aerosols and also by increasing the amount of carbon dioxide that remains in the atmosphere. Uncertainty about the magnitude of past and present cooling, however, means that we cannot be certain about the strength of future warming, which may exceed previous estimates.

Prof. Meinrat O. Andreae of the Max Planck Institute for Chemistry in Germany, Dr. Chris Jones from the Met Office's Hadley Centre for Climate Prediction and Research, and Prof. Peter Cox from the Centre for Ecology and Hydrology have studied the consequences of the cooling effect from man-made aerosols (tiny airborne particles) on present and future climate, and on the uptake of carbon dioxide CO2 by the land biosphere.

Such aerosols have reduced the amount of the sun's radiation that reaches the Earth's surface, and thereby have offset some of the warming impact of greenhouse gases - such as carbon dioxide - which have warmed the global climate during the 20th century. However, their harmful effects on air quality and human health have led to clean air legislation requiring us to clean up our emissions.

This necessary reduction in aerosols will result in a reduction of their cooling effect and hence will accelerate global warming. Dr. Jones likens this to driving a car whilst pressing both the accelerator and the brake, “Now we are taking our foot off the brake, but we don't know how fast we will go. Because we don't know exactly how strong the aerosol cooling has been, we do not know how strong the greenhouse warming will be”.

Any such warming will be further amplified by interactions between the climate and the carbon cycle - i.e., the Earth's natural biosphere. Ocean and land based ecosystems presently absorb about half of our CO2 emissions, but the impact of climate change will be to reduce this natural buffering service. “Higher temperatures mean dead matter decays faster”, explains Prof. Cox, “so if future warming is greater than expected, due to declining aerosol cooling, less CO2 will be taken up by the land, which will leave more CO2 in the atmosphere where it can add to greenhouse warming”.

The authors of the paper recognise the uncertainties, but maintain that this is a reason for action rather than inaction to cut global CO2 emissions. That’s because aerosol uncertainties act to increase the upper estimate of 21st century climate change without impacting on the lower estimate. As Prof. Andreae puts it: “The policy implications of even a 5-6 ºC temperature increase, comparable to the temperature rise from the previous ice age to the present, are enormous. Given the very grave potential consequences for the Earth’s environment and human society, the only prudent course of action would be to immediately reduce the emissions of climate-warming substances, with reduction targets well below those of the Kyoto protocol.”

The research was funded by the German Max Planck Society, the UK Department for Environment, Food and Rural Affairs under its Climate Prediction Programme, and the Natural Environment Research Council (NERC), and will be published on 30th June in Nature.

Source: Natural Environment Research Council (NERC)

Explore further: California 'rain debt' equal to average full year of precipitation

Related Stories

Making Europe sweat

July 21, 2015

In 2003, Europe experienced a record-breaking summer, and many people feel that this summer is headed the same way. In the midst of this heatwave, the scientific journal Nature Geoscience has published a study that can help ...

Japan pledges 26% emissions cut by 2030

July 18, 2015

Japan, the world's sixth biggest greenhouse gas polluter, has pledged to cut emissions 26 percent from 2013 levels by 2030, a target observers judged inadequate to avert calamitous global warming.

Recommended for you

Magnetism at nanoscale

August 3, 2015

As the demand grows for ever smaller, smarter electronics, so does the demand for understanding materials' behavior at ever smaller scales. Physicists at the U.S. Department of Energy's Ames Laboratory are building a unique ...

How the finch changes its tune

August 3, 2015

Like top musicians, songbirds train from a young age to weed out errors and trim variability from their songs, ultimately becoming consistent and reliable performers. But as with human musicians, even the best are not machines. ...

Study calculates the speed of ice formation

August 3, 2015

Researchers at Princeton University have for the first time directly calculated the rate at which water crystallizes into ice in a realistic computer model of water molecules. The simulations, which were carried out on supercomputers, ...

0 comments

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.