Lai See | Can climate science predict the future with confidence?

Our attention has been drawn to a piece that has appeared in a number of newspapers that attempts to inject a note of reality into the public discussion of climate change.

The subject of climate change is one that, as we have discovered, generates considerable heat. Much of this is directed at the messenger rather than the content and we expect more of the same.

The author is Steven Koonin, a former undersecretary for science in the US Department of Energy during President Barack Obama's first term and director of the Centre for Urban Science and Progress at New York University. He was previously professor of theoretical physics at the California Institute of Technology and chief scientist at BP, where he worked on renewable and low-carbon energy technologies.

He starts by noting the idea that "climate science is settled" runs through today's policy discussions. Unfortunately, that claim is misguided. He goes on to make the point that the crucial scientific question for policy is not whether climate is changing. It always has and always will. Nor is the crucial question about whether humans are influencing the climate.

He says there is little doubt that greenhouse gases mostly due to carbon emissions are influencing the climate. But "the impact today of human activity appears to be comparable to the intrinsic, natural variability of the climate system itself".

For Koonin, the crucial scientific question for policy is how the climate will change during the next century under both natural and human influences.

He says that although humans have some influence on the climate, it is small in relation to the climate as a whole. Human additions to atmospheric carbon dioxide are expected to shift its natural greenhouse effect by only 1 to 2 per cent. "Since the climate system is highly variable on its own, that smallness sets a very high bar for confidently projecting the consequences of human influences."