Climatologist Patrick J, Michaels writes in WSJ:
An East Coast blizzard howling, global temperatures peaking, the desert Southwest flooding, drought-stricken California drying up—surely there’s a common thread tying together this “extreme” weather. There is. But it has little to do with what recent headlines have been saying about the hottest year ever. It is called business as usual.
Surface temperatures are indeed increasing slightly: They’ve been going up, in fits and starts, for more than 150 years, or since a miserably cold and pestilential period known as the Little Ice Age. Before carbon dioxide from economic activity could have warmed us up, temperatures rose three-quarters of a degree Fahrenheit between 1910 and World War II. They then cooled down a bit, only to warm again from the mid-1970s to the late ’90s, about the same amount as earlier in the century.
Whether temperatures have warmed much since then depends on what you look at. Until last June, most scientists acknowledged that warming reached a peak in the late 1990s, and since then had plateaued in a “hiatus.” There are about 60 different explanations for this in the refereed literature.
NOAA’s alteration of its measurement standard and other changes produced a result that could have been predicted: a marginally significant warming trend in the data over the past several years, erasing the temperature plateau that vexed climate alarmists have found difficult to explain. Yet the increase remains far below what had been expected.
It is nonetheless true that 2015 shows the highest average surface temperature in the 160-year global history since reliable records started being available, with or without the “hiatus.” But that is also not very surprising. Early in 2015, a massive El Niño broke out. These quasiperiodic reversals of Pacific trade winds and deep-ocean currents are well-documented but poorly understood. They suppress the normally massive upwelling of cold water off South America that spreads across the ocean (and is the reason that Lima may be the most pleasant equatorial city on the planet). The Pacific reversal releases massive amounts of heat, and therefore surface temperature spikes. El Niño years in a warm plateau usually set a global-temperature record. What happened this year also happened with the last big one, in 1998.
Global average surface temperature in 2015 popped up by a bit more than a quarter of a degree Fahrenheit compared with the previous year. In 1998 the temperature rose by slightly less than a quarter-degree from 1997.
Without El Niño, temperatures in 2015 would have been typical of the post-1998 regime. And, even with El Niño, the effect those temperatures had on the global economy was de minimis.