The latest analysis of land-surface temperature by Berkeley Earth shows that the rise in average world land temperature is approximately 1.5 degrees C in the past 250 years, and about 0.9 degrees in the past 50 years. And, to the relief of IPCC, they claim that humans are responsible for the increase in temperature especially in the last 50 years.
It notes:
The annual and decadal land surface temperature from the BerkeleyEarth average, compared to a linear combination of volcanic sulfate emissions and the natural logarithm of CO2. It is observed that the large negative excursions in the early temperature records are likely to be explained by exceptional volcanic activity at this time. Similarly, the upward trend is likely to be an indication of anthropogenic changes. The grey area is the 95% confidence interval.
Richard A. Muller, a professor of physics at the University of California, Berkeley writes in the NYT:
The Conversion of a Climate-Change Skeptic
By RICHARD A. MULLER
CALL me a converted skeptic. Three years ago I identified problems in previous climate studies that, in my mind, threw doubt on the very existence of global warming. Last year, following an intensive research effort involving a dozen scientists, I concluded that global warming was real and that the prior estimates of the rate of warming were correct. I’m now going a step further: Humans are almost entirely the cause.
My total turnaround, in such a short time, is the result of careful and objective analysis by the Berkeley Earth Surface Temperature project, which I founded with my daughter Elizabeth. Our results show that the average temperature of the earth’s land has risen by two and a half degrees Fahrenheit over the past 250 years, including an increase of one and a half degrees over the most recent 50 years. Moreover, it appears likely that essentially all of this increase results from the human emission of greenhouse gases.
These findings are stronger than those of the Intergovernmental Panel on Climate Change, the United Nations group that defines the scientific and diplomatic consensus on global warming. In its 2007 report, the I.P.C.C. concluded only that most of the warming of the prior 50 years could be attributed to humans. It was possible, according to the I.P.C.C. consensus statement, that the warming before 1956 could be because of changes in solar activity, and that even a substantial part of the more recent warming could be natural.
With more emphasis, again, from their research:
The historic temperature pattern we observe has abrupt dips that match the emissions of known explosive volcanic eruptions; the particulates from such events reflect sunlight and cool the Earth’s surface for a few years. There are small rapid variations attributable to El Nino and other ocean currents such as the Gulf Stream. The gradual but systematic rise of 1.5 degrees C is best explained by the record of atmospheric carbon dioxide, measured from atmospheric samples and air trapped in polar ice.
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