Dr. David Whitehouse:
“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.
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.