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Global warming: top ten climate science questions

29.11.2010 14:48 Age: 7 yrs
Category: Climate change
By: Leon Clifford

Reporting Climate Science .Com's top ten list of climate change questions facing climate scientists as government officials and policy makers from around the world meet in Cancun.

With global climate policy makers debating the issues of emission reduction at Cancun, Reporting Climate Science .Com surveys some of the key outstanding questions in the science of climate change. Progress on understanding the issues raised by these questions will help reduce the areas of scientific uncertainty and so better inform the policy makers.

This is not an exhaustive list and others might well come up with a different set of questions. But all the questions on this list arise from current peer-reviewed scientific literature or have been raised by reputable climate scientists.

1.Where is the missing energy?
2.How do we reconcile plant and ice core evidence about carbon dioxide levels?

Carbon dioxide levels were flat and low prior to the industrial revolution, according to the ice core records that are referenced by the Intergovernmental Panel on Climate Change. Yet analysis of plant remains by reputable scientists shows significant variability in carbon dioxide levels since the last ice age. They can't both be right. We need to better understand the science of the history of atmospheric carbon dioxide levels.

3.What role do clouds play in global warming?

Specifically: does the global shortwave cloud forcing due to the enhancement of planetary albedo exceed in magnitude the longwave cloud forcing resulting from the greenhouse effect of clouds and how might this change in a warmer world? The case for global warming assumes that net cloud feedbacks are positive and some research suggests that they may become more positive with global warming. There is also evidence to suggest that the net forcing from clouds can be negative. We need to understand clouds much better.

4.How can we reduce uncertainties in the surface temperature record?

The temperature record is vital to understanding the issue of climate change for climate scientists looking at climate sensitivity issues, for policymakers trying to agree on an international response as well as for public awareness and information. The UK Met Office has recently said that it would be adjusting temperature change estimates upwards in the light of the discovery of a bias in sea surface temperature measurements. Temperature trend data prior to 1850 depends on reconstructing a record from proxy data and has been the subject of considerable controversy. We need to improve both current global monitoring and demonstrably reduce the uncertainties around the historical data.

5.What role do long term variations in the oceans play in the climate?

The El Nino and La Nina Pacific Ocean warming and cooling events have a measurable impact on the climate. But there are longer term ocean processes at work including the Pacific Decadal Oscillation and occasional changes in the North Atlantic conveyor or Gulf Stream. We need to fully understand all these processes.

6.What exactly happens at the end of ice ages and how do ice ages begin?

There is a lot more to ice ages than orbital factors. They involve complex and inter-related changes in temperature, atmospheric carbon dioxide levels and possibly methane too, as well as changes in ocean circulation patterns and sea level. An improved ability to model and explain what happens at the boundary of glacial and interglacial periods would give climate scientists even more confidence in our current theories.

7.How can we improve our confidence in multi-decadal models and regional climate models?

Reliable regional climate models and reliable long-term forecasts are vital to help inform policy makers. However, reputable climate scientists have raised doubts about our ability to reliably model regional-scale and multi-decadal changes with confidence.

8. Exactly how do ocean-air and land-air carbon fluxes vary ?

The proportion of emitted carbon dioxide that was absorbed by the land and by the oceans increased in 2009, according to research just published in Nature Geoscience. We know very precisely how much carbon dioxide is in the air and by how much that changes. We know much less about the exchanges between the air and the oceans and the air and the land and how these change.

9.How can we improve our understanding of the sun?

Most climate scientists do not think the sun plays a significant role in climate change but a number of potential links have been proposed. And some research published by Nature in October 2010 suggests that we do not know as much as we thought about how the sun works. The sun is a vital component of the climate system. To be confident about its impact on the climate system we need to be confident that we fully understand our nearest star.

10. How can we improve our understanding of all the complex interactions between humanity and the climate system?

Human civilisation does a lot more than just pump out carbon dioxide. How diverse are the human influences on the climate system and how significant are these various influences which include carbon dioxide emissions but may include other significant climate forcing mechanisms? A proper understanding of climate change requires a much fuller knowledge of the total impact of humanity on the climate.


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