Global climate change

Has Global Warming come to a Halt?

2/10/2012, 7:15:04 AM

Based on the trend in global temperature anomalies over the past decade, some have concluded that global warming has effectively "stopped".

In response to these claims, NASA scientists have presented reasons for this latest leveling out of the global temperature and a lot of it has to due with the strong interannual variability of the El Nino and La Nina phases.

Note the important graph from NASA.

590x331_02101703_feb10fig7


Excerpts from NASA GISS below......

Hansen et al. (2010) showed that the correlation of 12-month running-mean global temperature and Niño 3.4 index is maximum with global temperature lagging the Niño index by 4 months. Thus the 1997-1998 "El Niño of the century" had a timing that maximized 1998 global temperature. In contrast, the 2011 global temperature was dragged down by a strong La Niña. Indeed, the strength of the current double-bottomed La Niña, being based on ocean surface temperature relative to base period 1951-1980, is under-emphasized by the long-term trend toward higher temperature.

Thus, although the current global warming graphs are suggestive of a slowdown in global warming, this apparent slowdown may largely disappear as a few more years of data are added. In particular we need to see how high global temperature rises in response to the next El Niño, and we also need to consider the effect of the 10-12 year cycle of solar irradiance. Dr. James Hansen and others were on to something back in 2010........

Hansen et al. (2010) argued, in anticipation of the inevitable shift from the then beginning La Niña to the next El Niño, that "The 12-month running mean global temperature in 2010 has reached a new record level for the period of instrumental data. It is likely that the 12-month mean will begin to decline in the second half of 2010. The subsequent minimum in the 12-month running mean is likely to be in 2011-2012 and not as deep as the 2008 minimum. The next maximum, likely to be in 2012-2014, will probably bring a new record global temperature, because of the underlying warming trend."

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

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Global climate change