Monday, 10 December 2012

FAR out - have "climate change projections come true"?

Have they? Is what The Conversation claims that "20 years on, climate change projections have come true" correct?
Climate change predictions made 20 years ago have so far proved accurate, suggesting that the world is indeed on track to a radical climate shift, according to a new paper published today.
In 1990, the Intergovernmental Panel on Climate Change (IPCC) — a group of the world’s top climate scientists — released its First Assessment Report, predicting global warming of about 1.1 degrees celsius between 1990 and 2030.
In today’s edition of Nature Climate Change, climate scientists David Frame and Dáithí A. Stone argue that, halfway through that projection period, the predictions made in 1990 are proving mostly accurate.
The 1990 report’s “best estimate” was that the world would warm by about 1.1 degrees celsius between 1990 and 2030, meaning that the halfway prediction would be about 0.55 degrees celsius by 2010.
In fact, the world has now warmed by about 0.39 degrees celsius, coming very close to the prediction despite several unforeseen historical events, such as the collapse of the Soviet Union, the Mt Pinatubo volcanic eruption and the rise of China.
If I wanted to quibble (and of course I do) then firstly 1990 isn't quite "20 years ago", unless this article has been in the pending tray for a couple of years. I can do big sums like 2012-1990 = 22. Secondly, and more importantly, I've read the relevant bits of the iPCC First Assessment Report (FAR - in the post title, it's a pun - see?) and the figure 1.1 and the year 2030 don't ring a bell. The Overview for the FAR states
1.0.3 Based on current model results, we predict:
An average rate of increase of global mean temperature during the next century of about 0.3°C per decade (with an uncertainty range of 0.2—0.5°C per decade) assuming the IPCC Scenario A (Business-as-Usual) emissions of greenhouse gases; this is a more rapid increase than seen over the past 10,000 years.
This will result in a likely increase in the global mean temperature of about 1°C above the present value by 2025 (about 2°C above that in the pre-industrial period), and 3°C above today's value before the end of the next century (about 4°C above pre-industrial). The rise will not be steady because of other factors.
The Policymakers Summary for WGIII states in the Executive Summary
Based on current model results, we predict under the IPCC "Business-as-Usual" emissions of greenhouse gases, a rate of increase of global mean temperature during the next century of about 0.3°C per decade (with an uncertainty range of 0.2°C to 0.5°C per decade), greater than that seen over the past 10,000 years; under the same scenario, we also predict an average rate of global mean sea level rise of about 6 cm per decade over the next century (with an uncertainty range of 3-10 cm per decade).
So the FAR actually effectively predicted 0.6°C by 2010, not 0.55°C, yet even if it was as claimed 0.55°C then an actual rise of 0.39°C is just 70% of the prediction, which is therefore 41% above actual. That result is called "accurate"?
“As is always the case in science, we cannot know for certain that the 1990 prediction was accurate for the right reasons but, given the apparent absence of any credible alternative theories and the robustness of the prediction, this evaluation strongly supports the contention that the climate is responding to enhanced levels of GHGs (greenhouse gases) in accordance with historical expectations,” the authors wrote.
Low marks for accuracy, but an "A" in chutzpah, I'd say.
Penny Whetton, Senior Principal Research Scientist at the CSIRO and a lead author for the Third Assessment Report of the (IPCC), said the paper confirmed that “projections that climate scientists have been making have been accurate.”
“There are implications for the wider community for how they accept the IPCC conclusions. This is good evidence to show that what the IPCC has been saying for a while is coming true,” she said, adding that the discrepancy between the 0.55 degree projected rise and the 0.39 actual rise was explained by variability in estimates due to natural fluctuations.
“Once you allow for that, this paper demonstrates that the warming we are seeing is consistent with the projections made by the IPCC,” said Dr Whetton.
Err no, dear (I can be very condescending when the moment arrives) - estimates aren't subject to "natural fluctuations", it's reality that's subject to that. Once estimates are made, they're set in stone, see? Those who made them are stuck with them for ever more, except one Paul Ehrlich, of course - he just forgets he made 'em and carries on as if nothing different had happened. Oh - and Tim Flannery, of course who just claims he never said what he's recorded as saying on TV, radio and in newspapers, magazines, internet articles, blogs and St. Peter's great book of everything, for all I know. Then there's James Hansen who still stands by his prediction that the "Big Apple" would be 80 feet underwater by now (or next year, or something). He must have had his fingers crossed when Sandy's storm surge swept through Manhattan.

But I digress (cut me some slack, it's one of my few sources of amusement during these dark days of Armageddon predictions) - if a 30% error, on their own figures is considered accurate and "consistent with projections", where does that leave "Post-normal science"? If I'm given 39p change when I'm expecting 55p, am I justified in complaining, or do i have to accept it's "consistent with projections"?
Steve Sherwood, Co-Director, Climate Change Research Centre at the University of New South Wales said the paper showed “that if you take natural year-to-year variability into account in any reasonable way, the predictions are as close as one could reasonably expect.”
“Those who have been claiming ad nauseum that the climate models have been proved wrong, should read this paper, even though for most of us it is not very surprising,” said Dr Sherwood, who was not involved in the Nature Climate Change paper.
“Though there is no contrarian analogue to the IPCC, individual contrarians have made predictions over a similar time frame that the warming would stop or reverse. The data since then have probably falsified many of those predictions (which the deniers continue to make today).”
I don't need to "read this paper", I just need to read a global temperature dataset - any dataset, GISS included. Obviously, people like Sherwood don't need to do that, they just announce that the Emperor's New Clothes are a remarkable fit, despite the fact that the proles are giggling and pointing at his projections.

Shoot an arrow in the air, and where it lands call that the target, and announce it's "accurate" - it'll do for the proles and politicians.

No comments:

Post a Comment