Apologies for the delay on this article. We’ve now fixed the weblog issue
The BBC reports on yet another discovery of the "Smoking Gun" of anthropogenic global warming.
The Earth is absorbing more energy from the Sun than it is giving back into space, according to a new study by climate scientists in the US.
They base their findings on computer models of climate, and on measurements of temperature in the oceans.
The group describes its results as "the smoking gun that we were looking for", removing any doubt that human activities are warming the planet.
The results are published in the journal Science this week.
The study attempts to calculate the Earth’s "energy imbalance" – the difference between the amount of energy received at the top of the atmosphere from solar radiation, and the amount that is given back into space.
Rather than measuring the imbalance directly, the researchers draw on data from the oceans, in particular from the growing global flotilla of scientific buoys and floats, now numbered in the thousands, which monitor sea temperature.
And it’s co-authored by our friend from realclimate, Dr Gavin Schmidt:
"Measuring the imbalance directly is extremely difficult, because you are looking for a very small number on a background of very large numbers," Gavin Schmidt, one of the research team from the US space agency’s (Nasa) Goddard Institute for Space Studies in New York, told BBC News.
Yes, we’ll come back to you on that one. So, how long is the baseline for these measurements?
"But we know how much energy is going into the oceans – that has been measured and over the last 10 years confirmed by satellites and in-situ measurements – and from our understanding of atmospheric physics, that has to be equal to the imbalance at the top of the atmosphere."
Yep, a whole ten years. Not even one solar cycle. The satellite record is 26 years long, but they looked at ten.
Bob Park in his latest "What’s New" newsletter showed exactly the length of the ocean measurements used:
A week ago, an important editorial in Science by Donald Kennedy
called attention to NASA’s recent decision to delay or cancel
planned Earth science missions and terminate orbiting spacecraft
to feed the pointless Moon/Mars mission. A report in this week’s
Science shows how just short sighted that is. An international
monitoring effort, Argo, has deployed 1,800 instrumented floats
in oceans around the world since 2000. A NASA team led by James
Hansen collected data from the floats and precisely determined
ocean levels from satellite observations. They found that Earth
is absorbing more energy than it’s radiating back into space, an
imbalance large enough to raise temperatures 1 F this century,
even if greenhouse gas emissions are capped tomorrow. "There can
no longer be genuine doubt that human-made gases are the dominant
cause of observed warming," Hansen said. "This energy imbalance
is the ‘smoking gun’ that we have been looking for."
A whole four-and-a-bit years of ocean observations.
Back to the BBC article:
So data gathered from the oceans is plugged into a computer model representing the Earth’s complex climate, including the atmosphere, oceans, winds, currents, greenhouse gases and other "pollutants". What emerges is that at the top of the atmosphere, our planet is absorbing 0.85 watts more energy per metre squared than it is emitting into space.
So the energy is out of balance in the short time frame considered and no solar variation is mentioned at all. Any chance of some wild extrapolation?
"The normal state of the atmosphere is that pretty much the same amount of energy that comes in leaves; and only when there are very large changes is that going to change.
"Historically, those changes have happened very slowly; but what we are doing now is we are changing that imbalance at a rate which appears to be unprecedented over at least a thousand years and possibly longer."
From ten years to a thousand. Of course, proof of Gavin’s statement about it being "unprecedented over at least a thousand years" is strangely absent from the report published in Science, but maybe I’m not reading between the correct lines. Could Gavin be trying to throw another lifeline to the Hockey Stick?
Next comes the traditional BBC Online climate skeptic sandwich. This week, the lucky winner is William Kininmonth:
Not everyone agrees with these conclusions. One scientist who disagrees is William Kininmonth, a former head of Australia’s National Climate Centre and a member of Australia’s delegations at various rounds of United Nations climate treaty negotiations.
"The paper implies that it is possible to estimate quite accurately the global radiation imbalance," he told BBC News; other researchers, he says, have "explained why it is not possible to measure the imbalance with an accuracy better than several watts per metre squared".
Like other "climate change sceptics", Dr Kininmonth believes too much reliance is placed on computer models rather than hard data.
"I do not believe this research team has made a compelling case to suggest that their computer models are sufficiently realistic to justify the implications of anthropogenic (human-induced) global warming that they make," he said.
Oh don’t be such a wet blanket, William. Don’t you know that climate models can find signals much smaller than the resolution of the measurements? Yes, I know that even the IPCC warns that climate models are "unfalsifiable in the strict Popperian sense", but that’s the genius: no-one can prove them wrong.
Back to the cheering:
But Damian Wilson, manager of clouds and radiation parameterisation at the UK’s Meteorological Office, was more enthusiastic.
"The computer model matches temperature changes at the Earth’s surface quite well – but that alone doesn’t prove it’s right," he said.
"Having a model that also matches ocean heat uptake well suggests that the model is doing a pretty good job. I wouldn’t like to say the research proves that 0.85 watts per metre squared is the right figure, but it does give us more confidence that the models are doing a good job of producing a reasonable simulation of the energy imbalance."
Well that’s a half cheer, actually. Not that enthusiastic.
Has it occurred to anyone that that the Earth must be out of radiative balance by small smounts at some stages because the feedbacks and secondary responses are not instantaneous? Or that the cooling of Antarctica over the last 50 years and the growth of the icesheets practically everywhere except the tiny Antartic Peninsula represent a large sink sucking heat out of the atmosphere? Since the report excluded the poles from the analysis, is it any wonder they failed to mention this?
Personally I wonder what the gun is smoking, but that’s just me…