Global warming: Just how warm?

All but one of the 13 warmest years worldwide have occurred in the 21st Century, according to the National Climate Data Center, the lone exception being 1998.

The U.N. World Meteorological Organization's rankings are similar. The WMO announced yesterday that 2012 was the ninth-warmest year in its data set, which goes back to 1850. The climate center has it at No. 10, in data that starts with 1880.

In the first quarter of 2013, world temperatures were 1.04 degrees Fahrenehit above the 20th Century average, 57, almost precisely what the anomaly was for all of  2012, according to the climate center.

The world certainly is warmer than it was in the 19th Century, and the pace accelerated iin the late 20th, but in recent years, the data show, the warming rate has slowed.

The 2012 temperature was nearly the same as 2011's, and both were significantly lower than 2010's, points out James Hansen, the former NASA scientist who has long been one of the most-visible scientists in the climate change arena.

In his annual report, Hansen addressed what he called the "standstill" issue, stating, "The fiive-year running mean of global temperature has been flat for the past decade."

However, Hansen said that trend is unlkely to continue, and one reason is linked to the aforementioned 1998, No. 3 on the climate center list.

That year, a record El Nino -- an anomalous warming of survace waters over a vast expanse of the tropical Pacific -- bumped up the global temperature. 

El Ninos and their mirror opposities -- the anomalous cooling of La Nina -- clearly influence the outcome of global temperature calculations.

In three of the last five years, the annual world temperature dropped from the previous year. In the period, the Pacific was in an official state of La Nina 29 months, compared with 10 months for El Nino, a mix that is likely to change.

Hansen said that it's possible that "a slowdown in climate forcing growth rate" has contributed to cooling the warmng rate, but "We conclude that background global warming is continuing,"

In any event, we would be surprised if 2013 did not finish in the top 10, and absolutely shocked if it wasn't in the top 25.

The biggest annual increase we found in the government's data -- again, these temperatures are computed through a complicated process from worldwide measuring stations -- was 0.45 degrees from 1976 to 1977.

Interestingly, the biggest decrease was roughly the same, 0.47 degrees, from 1963 to 1964.

Given how warm it has been, even if 2013 experienced a decrease of that '60s level -- and that's extremely unlikely -- it would still finish in the top 25, El Nino or no El Nino.