Sunday, January 24, 2016

David Whitehouse: 2015 Global Temp, Or How Some Scientists Deliberately Mistook Weather For Climate

The data for the global temperature of 2015 is in, and its a shattering record. It is claimed that global warming has resurged, terminating the warming ‘pause’ for good. But an important factor has been downplayed and one ignored altogether.

Nasa says that 2015 was 0.13°C+/-0.10°C above 2014. The UK Met Office said that 2015 was 0.18°C +/- 0.10°C above 2014. Noaa says 2015 was 0.16°C+/-0.09°C warmer than the previous record which was 2014.

Noaa had only one month in 2015 cooler than the same month in 2014 – April. According to the Nasa data four of them were cooler than 2014 (April, May, Aug, Sept) whilst Hadcrut4 had eleven months warmer than 2014 with April tied. For September 2015 Nasa has it 0.08°C cooler than 2014 whereas Noaa has it 0.14°C warmer!

Despite what some scientists have said the large increase over 2014 is far too great and swift to be due to a resurgence of forced global warming. It must be due to short-term natural variability, and you don’t have to look far to find it. 2015 was the year of the El Nino which boosted the year’s temperature. (In the Nasa press conference about the 2015 global temperature see how long it takes the presenters to mention the El Nino).

“We are seeing an extreme climate state,” Randall Dole, a meteorologist working for Noaa, told the Journal Nature this week. He was commenting on the recent El Nino which is one of the strongest on record, with ocean temperatures reaching as much as 3°C above normal in parts of the central and eastern Pacific. It was unsurprising then that Nasa on releasing its global temperature measurements made reference to it. “Only once before, in 1998, has the new record been much greater than the old record by that much.” This clearly because 2015 was like 1998 a strong El Nino year.

One point to notice however is that even without the El Nino that made the fourth quarter much warmer than the preceding three 2015 would have been a record for the Nasa data. If the first six months of the year had been repeated then it would still have set a record. Curiously though no single month during that period (indeed up to September) set a record for that particular month demonstrating how close the global temperature has been over the past decade or so.

If the El Nino dominated the last part of the year another example of natural variability was dominating the earlier months. The reason for the first nine months of 2015 being collectively warm can also be found in the Pacific. As I reported in September 2015 conditions in the north Pacific were unprecedented in 2015. The Summer warmth of 2014 had not dissipated. Indeed since 2013 the so-called Pacific “Blob” has kept a million square km of ocean 3°C above normal, (indications are that as of January 2016 the blob is beginning to dissipate.) “The temperatures are above anything we have seen before,” said one scientist in my article.

So 2015 was an exceptional year for weather, which is not the way some scientists presented it. None of them mentioned the “blob” and as for the El Nino it was the “little bit on the top” merely a minor contribution. Most of the temperature rise was down to forced global warming, they said.

This is all slight of hand, and a little inaccurate. The IPCC says that just over half of the warming since the fifties is forced so most of the contribution to 2015′s temperature is natural variability. In addition the factor that makes 2015 warmer than its previous years is not a resurgence of forced global warming but the “blob” and the El Nino.

One can speculate what the temperature of 2014 and 2015 would have been without the blob and the El Nino. Some scientists have said it made only a few hundredths of a degree difference, others have said it makes a few tenths of a degree difference.

I think the few hundredths of a degree suggestion is wrong. So can the combined “blob” and El Nino account for the 2015 temperature excess of 0.13, 0.18 or 0.16°C depending on your choice of data set? It could. Indeed without the “blob” and the El Nino 2015 could have been cooler than 2014. Without the “blob” 2014 could have been cooler than 2010.

This makes suggestions that the “pause” in annual average global surface temperatures has been “terminated” premature. The “pause” will not be ended by weather but by forced global warming. Consequently it is unsafe to use 2015 in any trend analysis to eliminate the “pause.” It is essential to view the 2015 along with subsequent years to catch the cooling La Nina effect. Only this way can the El Nino contribution be properly assessed.

The main conclusion that can be drawn about 2015 is that it was a truly exceptional year for weather, and for misleading press releases.

Dr David Whitehouse is the Science Editor of the London-based Global Warming Policy Forum - feedback:

No comments: