Has global cooling begun?

Taking the long-view temperature trends since the Industrial Revolution. The data come from NASA's Goddard Institute for Space Studies in New York. The red line teases the trend out of the ups and downs of global average temperatures. Global cooling started in the first decade of the 21st century? Certainly not in the context of the past century.

Yikes! On Sunday, Oct. 18, the New England Patriots were playing at home, in Foxboro, Mass., in a snowstorm that made it look more like a January game! Global warming must be over!

So many people wish that global warming would just go away. But sorry. It ain't happenin'. The atmosphere, if it could talk, is refusing to say: Uncle! At least to those wishing the issue would disappear.

The latest deuce in the global-cooling house of cards came recently via the BBC. One of The Monitor's reporters recapped it here. What climate data actually has to say about the issue appears here and here.

But if you want to save a mouse click or two, here's the upshot: The most that can be said is that natural variability may well have been strong enough to slow for the past 11 years any signal from human-induced warming.

Ironically, Britain's Hadley Center for Climate Prediction and Research, the former employer of the local BBC weatherman who patched the BBC article together under the title of "climate correspondent," has this to say about the current state of the climate:

The record-breaking temperatures in 1998 occurred after three decades of warming, starting in the 1970s. These decades saw an increase in global average temperature of about 0.45 °C. After 1998, however, warming slowed significantly — trends over the past 10 years show only a 0.07 °C increase in global average temperature. Although this is only a small increase, it indicates that there has been no global cooling over this period. In fact, over the past decade, most years have remained much closer to the record global average temperature reached in 1998 than to temperatures before the 1970s. All the years from 2000 to 2008 have been in the top 14 warmest years on record. (Here's the link.)

Moreover, Hadley researchers asked themselves the musical question: How often would one expect a brief respite from rising temperatures? Jeff Knight, who contributed to an exhaustive State of the Climate 2008 report that appeared in the August in the Bulletin of the American Meteorological Society, noted:

“We found about one in every eight decades has near-zero or negative global temperature trends in simulations which would otherwise be warm at expected present-day rates. Given that we have seen fairly consistent global warming since the 1970s, these odds suggest the observed slowdown was due to occur.” (Here's the link.)

You can download a PDF of the 199-page report here. No subscription is required.

Part of the challenge in thinking about global warming is the time scale involved. Global warming is a century(ies)-long process. Temporal context counts for a lot trying to decipher what's happening during any 10- or 11-year period.

This is illustrated by the temperature graph at the top of this post. It shows by how much global average surface temperatures have risen above or fallen below the 1951-1980 average each year.

The five-year running average (red trend line) from 1900 to about 1910? Oh, my gosh, global cooling! Maybe, maybe not. Looking at 1880 to 1910, not much of an overall trend there. Just ups and downs.

How about 1940 to around 1950? Oh, my gosh! Global cooling! Eh, not so much compared with the previous 60 years.

The cool spell from about the mid-1950s to around 1970? Global cooling! Eh, not so much compared with the previous 90 years; the trend is still up. And the bottom of the "trough" is warmer that the bottom of the preceding trough.

From around 1970 on? Temperature deviations from the norm continue to rise to a peak in 1998, then flatten for the ensuing period.

So, is there really enough in the last decade's worth of readings to pronounce the end of global warming and the beginning of global cooling. Eh, not so much.

Another challenge? Location, location, location.

People tend to think about global warming in terms of what's happening where they live or in their immediate region. That's natural. But just as global warming requires temporal context, it also requires geographic context -- we're talking the globe here, not just Foxboro, Mass. (It was a pretty spectacular football game if you're a New England fan!)

The global -- there's that word again -- surface-temperature maps that the National Oceanic and Atmospheric Administration published at summer's end (see second image above) show that much of the lower 48 states and up into Canada had a cooler-than-normal summer. It was the 34th coolest summer on record for the continental US as a whole.

But if you lived in Australia, you'd have quite a different take on temperature variations during the June-August period. There, it was much warmer than normal. The June-August period was the third warmest on record globally, NOAA reported.

El Niño undoubtedly played a role. But that's one of the gotchas of global warming. Natural climate swings such as El Niño wind up being superimposed atop the much-longer-term warming trend.

So, global cooling has begun, eh? Not likely.

Added later by editor: Statistics experts reject global cooling claims.

 You'll find numerous articles about the environment on the Monitor’s main environment page,. Also, check out our Bright Green blog archive and our RSS feed.

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