Extra climate targets urge faster CO2 cuts

University of Bern's Marco Steinacher has helped show that setting limits on different aspects of damage from climate change will likely limit CO2 emissions more than just temperature alone. Credit: University of Bern

University of Bern’s Marco Steinacher has helped show that setting limits on different aspects of damage from climate change will likely limit CO2 emissions more than just temperature alone. Credit: University of Bern

To give the world a chance of restricting damage caused by climate change, we need more than just a single temperature target, Swiss researchers have found. Marco Steinacher and his teammates at the University of Bern worked out the chances that climate change can be kept within harmful limits in six different areas. “Considering multiple targets reduces the allowable carbon emissions compared to temperature targets alone, and thus CO2 emissions have to be reduced more quickly and strongly,” Marco told me.

In December 2009, world leaders agreed the non-binding Copenhagen Accord, which ‘recognises’ that scientists think world temperature increases beyond 2°C above the pre-industrial average from 1850-1899 would be dangerous. It also mentions sea level rise, protecting ecosystems and food production. And as climate talks have continued since the 1990s, specific new dangers of CO2 emissions have been found. One serious impact that has been realised in the last decade comes from the fact that oceans absorb CO2 from the air, which makes the seas more acidic. That can make it harder for sea creatures’ shells to form, and together with warmer seas can damage coral, and in turn reduce fish numbers available for food. “Traditional climate targets have not addressed this effect,” Marco said.

It might seem reasonable to assume that negotiating climate deals on temperature limits alone could protect against other dangers. But until recently only very simple ‘Earth system’ models were available to test this against the idea of having several targets. They couldn’t simulate regional effects on quantities such as ocean acidification or farming productions, Marco said. “Climate targets that aim at limiting such regional changes can only be investigated with a model that has a certain amount of complexity,” he explained. Read the rest of this entry »

Saturday round-up: Breathing space on CO2 cuts?

As well as satellite measurements, US National Oceanographic and Atmospheric Administration researchers used balloons at a single site in Boulder, Colorado, to find out how much water is in the stratosphere. (Credit NOAA)

Two major papers this week suggest that global warming is likely to accelerate at a slower pace than had previously been thought. In the first, Susan Solomon of the US National Oceanic and Atmospheric Administration has identified a possible cause of lower temperature increases in the noughties compared to the nineties. In the second, David Frank of the University of Bern in Switzerland suggests that the effect of a natural process that worsens man-made climate change has been overstated.

Together with a different set of Bern researchers, Solomon and colleagues in Boulder, Colorado, have shed some light on the poorly understood impact of water in the stratosphere on the world’s temperature. Water vapour in the stratosphere – the layer of the atmosphere above that which we live in – is known to cool that part of the atmosphere down but warm the troposphere underneath. However, it’s taken having satellites floating around the planet to measure accurately how much water is actually there.

The period in which measurements have been possible includes the rapid warming of the 1990s, and slower warming since. Solomon and her colleagues’ measurements show that water concentrations were higher during the warm period, and lower during the cool period. Creating computer models from these data suggest that the drop in stratospheric water vapour after 2000 decreased the rate of warming compared to what would have been otherwise expected by about 25%. The 1990s increase in water vapour could “have steepened the rate of global warming from 1990–2000 by about 30%,” the January 29 Science paper says. The researchers point out that it’s not yet known whether this is a feedback through which the earth tries to cool itself, or something that changes periodically.

The previous day, Frank’s team’s Nature paper tackled the question of just how much CO2 is released from biological sources when the planet warms up, adding to what man is making by burning fossil fuels. “Approximately 40% of the uncertainty related to projected warming of the twenty-first century stems from the unknown behaviour of the carbon cycle,” they write. They evaluated all available large-scale temperature reconstructions and estimates of over the past thousand years. Their results suggest that the likely range of how much CO2 is put into the atmosphere for each degree of warming is likely to be in the lower half of current estimates.

Although neither Frank’s or Solomon’s research team suggests that global warming is about to reverse, taken together they might mean that humanity has longer to fight it than previously thought.

Another process currently helping to cool the globe is the formation of clouds under the ozone hole in the Southern hemisphere, researchers revealed in Geophysical Research Letters on Wednesday. Higher winds that are linked to ozone loss whip up more sea spray, which creates more clouds. These clouds reflect heat from the sun back out into space, helping counteract greenhouse-gas based global warming. The link between the winds that create clouds and ozone loss could lead to the strange situation where a fully-repaired hole could lead to faster worldwide temperature rises.

Outside of climate research this week, a Yale and Mason University survey of 1001 US adults shows that only 57% think that global warming is happening in 2010, compared with 71% in a similar survey in 2008. The proportion that think it is not happening has doubled over that period, to 20% now. Regardless of which side of this debate you stand on, the silver lining may be the reduced amount of stress global warming is now causing Americans: The number who say that they are “very worried” about climate change has fallen from 17% in 2008, to 12% today.