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Expert Commentary about 2012 Global Temperatures

February 1, 2013; 6:09 PM ET

Dr. James Hansen, who is the director of NASA's Goddard Institute for Space Studies (GISS) recently wrote a summary about the global temperature anomalies for 2012 with assistance from Dr. Makiko Sato and R. Ruedy.

Last year was the 9th warmest year on record globally, according to GISS. Records go back to 1880.

Image courtesy of GISS.

Below, Hansen makes some valid points about 2012 and temperature trends.......

The top 10 warmest years on record all occurred since 1998.

The 5-year mean global temperature has been flat for a decade, which they interprete asa combination of natural variability and a slowdown in the growth rate of the net climate forcing.

Short-term global fluctuations are associated principally with natural oscillations of tropical Pacific sea surface temperatures (El Nino/La Nina)

The long-term warming trend, including continual warming since the mid-1970's, has been conclusively associated with the predominant global climate forcing, human-made greenhouse gases, which grew steadily in the early 20th century.

The period of cooling that took place between 1940 and 1975 was likely attributed to a balance of aerosol cooling from low air pollution standards and greenhouse gas warming.

A slower growth rate of the net climate forcing may have contributed to the standstill of global

temperature in the past decade, but it cannot explain the standstill, because it is known that the planet has been out of energy balance, more energy coming in from the sun than energy being radiated to space. The planetary energy imbalance is due largely to the increase of climate forcings in prior decades and the great thermal inertia of the ocean. The more important factor in the standstill is probably unforced dynamical variability, essentially climatic "noise".

If solar irradiance were the dominant drive of climate change that most global warming contrarians believe, then a global cooling trend might be expected.

......the continuing planetary energy imbalance and the rapid increase of CO2 emissions from fossil fuel use assure that global warming will continue on decadal time scales.

Our interpretation of the larger role of unforced variability in temperature change of the past decade, suggests that global temperature will rise significantly in the next few years as the tropics moves inevitably into the next El Nino phase.

The one major wild card in projections of future climate change is the unmeasured climate forcing due to aerosol changes and their effects on clouds.

The "climate dice" are now sufficiently loaded that an observant person should notice that unusually warm seasons are occurring much more frequently than they did a few decades earlier.

The views expressed are those of the author and not necessarily those of AccuWeather, Inc. or AccuWeather.com

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