Tuesday, 17 September 2013

David Rose's HALF global warming claim and a HALF-witted spin-off.

David Rose in The Mail has done it again, managing to stir up a minor maelstrom in the world of climate change debate with his latest article claiming boldly that "Global warming is just HALF of what we [scientists] said". This seems to have upset quite a lot of people who claim that the headline is misleading and that, furthermore, claims made in the actual text of the article are factually incorrect - not an unheard of accusation re. David Rose climate-related articles it must be said!

The Telegraph ran a spin-off piece the very next day on the same theme, i.e. that scientists got it wrong on global warming.

Now, as a man-made climate change sceptic/contrarian, I am of course heartened to see, at long last, admissions in the mainstream press that predictions of anthropogenic CO2 induced warming have turned out to be grossly overestimated by the IPCC and others, which they have, no denying. However, I have to take issue with the manner in which Rose has chosen to write about this discrepancy because I believe, ultimately,  he fails to clearly inform the public of how exactly scientists got it wrong, and that is not a good thing when, at this critical juncture in the climate debate, we need scrupulous clarity. Having said that, the bulk of Rose's piece in the Mail is spot on, clear and precise, just not on the issue of observed and predicted warming over the timescales implied.

The Telegraph spin-off piece is one of the most shoddy examples of journalism I have seen in a while, to which I shall return presently.

Rose says: 

"The Mail on Sunday has obtained the final draft of a report to be published later this month by the UN Intergovernmental Panel on Climate Change (IPCC), the ultimate watchdog whose massive, six-yearly ‘assessments’ are accepted by environmentalists, politicians and experts as the gospel of climate science."

He refers of course to AR5, the much anticipated latest upcoming climate Assessment Report by the IPCC, which will form the basis of government policy decisions on climate change across the world. The last was AR4 in 2007 and it would seem that the IPCC have considerably altered their scientific appraisal of AGW since that time because the world's climate has steadfastly refused to behave as they originally predicted.

This is the passage that gets Rose into hot water. He says:

"Yet the leaked report makes the extraordinary concession that the world has been warming at only just over half the rate claimed by the IPCC in its last assessment,  published in 2007. 

Back then, it said that the planet was warming at a rate of 0.2C every decade – a figure it claimed was in line with the forecasts made by computer climate models.
But the new report says the true figure since 1951 has been only 0.12C per decade – a rate far below even the lowest computer prediction."

Firstly, commentators in the press and on Twitter and elsewhere have picked up on the supposed 'inaccuracy' of 0.12C/decade, claiming that Rose has got his figures wrong. This stems from the fact that in 2007 the IPCC stated that "The [observed] linear warming trend over the last 50 years [is] (0.13°C [0.10°C to 0.16°C] per decade)". Bear in mind that this is what the IPCC were saying in 2007, so it is entirely conceivable that the leaked AR5 report concludes that the average linear trend in warming since 1951 is now 0.12C per decade, virtually unchanged. So whence comes Rose's idea that warming is HALF of what the IPCC  stated in 2007? Commentators have jumped on this as evidence of the fact that Rose's statements are misleading/incorrect/ill-informed.

It is not at all clear whether Rose's leaked linear warming trend figure covers the entire period from 1951 to the present - we shall have to wait until the publication of the actual report to see exactly what period this covers. Note that in AR4 it was the 'last 50 years' which technically would cover 1957 to 2007. My guess is that the figure of 0.12C covers the period 1951-2010, but it may extend further. The point is, it's very confusing and not at all obvious exactly what Rose is trying to say.

So where does Rose get his figure of 0.2C from to enable him to claim that warming has been only half of what the IPCC said in 2007? From here probably. Note that this is the IPCC's projections of warming as opposed to their direct observations of warming which they equated to 0.13C per decade in 2007. They say:

"For the next two decades, a warming of about 0.2°C per decade is projected for a range of SRES emission scenarios."

BUT, and here is where it starts to get really confusing, they also state that:

"Since IPCC’s first report in 1990, assessed projections have suggested global average temperature increases between about 0.15°C and 0.3°C per decade for 1990 to 2005. This can now be compared with observed values of about 0.2°C per decade, strengthening confidence in near-term projections".

So, in essence the IPCC are stating that their predicted warming is 0.2C/decade and that actual warming over the period 1990 to 2005 is also 'about' 0.2C/decade. So this is very likely where Rose gets his info from but he compares this very inappropriately with the observed linear warming trend since 1951 leaked from AR5. The fact is, scientists have got it wrong in that they predicted far more warming than has actually taken place, just not in the way Rose is claiming, which is unfortunate, because I don't think Rose set out to deliberately mislead; he just failed to express clearly and coherently the actual situation, thereby providing opponents with ammunition to claim that he was 'wrong'.

Which brings me to the very sloppily written and ill-informed spin-off article in the Telegraph, penned by Hayley Dixon.

She states, ludicrously, that:
"The “summary for policymakers” of the report, seen by the Mail on Sunday, states that the world is warming at a rate of 0.12C per decade since 1951, compared to a prediction of 0.13C per decade in their last assessment published in 2007". 

The implication somehow is that this tiny difference is the basis for stating that scientists 'got it wrong' because there is no mention at all of the projected figure of 0.2C covering the period from 1990. Wrong. Wrong also in the fact that 0.13C was not a prediction in AR4 but an observation of an actual warming trend.

Quite how the IPCC could have predicted a linear increase in global temperatures covering a period from 1951 when they were not even in existence I have no idea, unless they are privy to the secrets of time travel yet to be released to the global community and availed themselves of this secret knowledge to make the trip back to 1951 - first erasing their actual knowledge of the observed warming trend of course, thereby ensuring that it would actually be a prediction!!

Dixon goes on to say:

Other admission in the latest document include that forecast computers may not have taken enough notice of natural variability in the climate, therefore exaggerating the effect of increased carbon emissions on world temperatures".

Let me rewrite that for you in plain English my dear:

Other admission[s] in the latest document include [the fact] that [computer forecasts] may not have taken enough notice of natural variability in the climate, therefore exaggerating the effect of increased emissions on world temperatures.