By JR on Saturday, June 11, 2011
Dr. David Whitehouse
If there is one question, in my experience, that many climate scientists will avoid it is, “how long does the current standstill in global temperatures have to continue before you question some of your assumptions about global warming?” The question is a pertinent one. In the past decade there is evidence that atmospheric carbon dioxide levels have increased more steeply than before, so why hasn’t the temperature gone up faster than ever before?
When it was first noted some years ago that the post 2001 global annual temperature was at a standstill it aroused considerable passion. Though it was a simple description of the data often those who pointed it out were severely criticised, and their motives questioned. Even today some deny there has been a standstill, although it is now accepted as fact in the scientific literature that the Earth has not warmed at all in the past ten years. See the references in the GWPF article "nothing wrong with our graph" as well as here, also Wang et al Advances in Climate Change Research 1(1): 49-54, 2010, and here, to give but a selection of many references. Even the Royal Society has said the rate of increase has slowed.
Some will say it’s meaningless as ten years is nothing, the canonical climate period is thirty years and that the 1980s were warmer than the 1970s, the 1990s were warmer than the 80s and the past decade is the warmest of the instrumental record. What more needs to be said?
One climate scientist even said that if the temperature stayed the same for the next 50 years it would make no difference to the theory.
But clearly it does matter. Whatever its relationship to long-term climate, the standstill is important because it requires an explanation, and because nobody predicted it, or indeed has a specific explanation for it.
Some will argue that more than a decade ago they correctly predicted the average temperature of the first decade of this century and that it proves the climate models are correct. However, predicting the decadal average temperature, extrapolated from the 1980s and 1990s as part of a rising trend in temperatures is one thing. Predicting that the temperature rise would stop for a decade is another entirely. Also predictions made a decade ago, especially if ‘successful’ must be considered in the light of climatic influences we have since discovered such as solar effects, revised recently, and stratospheric water vapour variations.
The fundamental observable, in the absence of other climatic influences, of increasing levels of greenhouse gasses is rising temperature. Sooner or later the other variations in climate will average out and the long-term greenhouse gas upwards trend must re-establish itself.
How long the standstill?
It is currently at ten years. If you look at the instrumental temperature record, HadCrut3 for example, it’s obvious that there are features in the temperature curve that each require an explanation. The initial low temperatures and rough standstill between 1850 – 1910 (there was a brief warmish phase at about 1875). The rise between 1910 and 1940, the standstill between 1940 – 1980, the rise 1980 – 2000 and the standstill 2000 – 2010. Standstills are not unusual. It is also interesting that in the 50 years since 1960 when the IPCC says greenhouse gasses became the dominant climate driver, there has been temperature increases in only two of five decades! In fact, since the start of the instrumental period in 1850 only 50 of the 160 years have been part of an increasing trend.
Recently the UK Met Office conducted a series of simulations incorporating climate change models with decadal fluctuations in climate and concluded that one out of every eight decades would show a ten-year standstill, but that no standstill will last as long as 15 years. Since we have three standstill decades since 1960 this data seems to be somewhat outside the conclusions of the simulations. Each year is now significant as a prolonged hiatus in temperature acquires more and more statistical significance in taking the observations away from the theoretical predictions.
Keenlyside et al predict no increase in global temperature over the next decade whilst Smith et al made predictions for post 2009 global temperatures saying that there would be a period of stability until 2009 and thence an increase with half of the subsequent years being warmer than 2009. It remains to be seen if this will be the case.
The IPCC says there should be an increase, on average, of 0.2 deg per decade. In Hadcrut3 the increase for 1979 – 2008 is 0.18 deg per decade which seems to fit in with the IPCC estimates. However, the trend for the past decade is zero making a revised estimate for the 1980 – 2000 period as 0.27 deg per decade.
Looking at atmospheric data, which is independent of the weather station data used in HadCrut3 (I am grateful to Lubos Motl for these figures), from RMS AMU between January 1979 and 2011 the increase was 0.14 deg per decade. However, the figure for 2001 – 2011 is minus 0.04 deg per decade. That is, if anything, the world has got cooler, although still within a statistical constant line within errors of measurement.
The UK Met Office has said that it believes the standstill is probably partly caused by the low solar activity of the past decade coupled with the influence of stratospheric water vapour variations. Only appreciated very recently these variations have had the effect of reducing the increase in the past decade. However, if this is accepted then it must also be accepted that the same variations added up to a third of the temperature increase seen between 1980 – 2000.
In its last report the IPCC showed a graph showing global surface warming vs date for various greenhouse gas emission scenarios. Curiously, for a report issued in 2007, it used only global temperature data up to 2000, that is before the standstill. The actual trajectory taken by the world’s temperature is much closer to the temperature expected for constant greenhouse gas concentrations at the 2000 level, which is obviously not what is happening to our atmosphere. None of the IPCC’s scenarios are consistent with the observed global temperature standstill.
When the IPCC issues an update to this graph in their next report they should use the data up to 2010 with data that includes the standstill.
Perhaps it is temporary and a regular feature of an intermittently warming world, perhaps it is not, the global temperature standstill of the past decade is real and contains information that is crucial to the debate about global warming.
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