Global warming ‘pause’ — warmest 17 years on record, by far

Originally published in The Aquarian, Spring 2015.

The Warmest Year(s) on Record

2014 may not be the warmest year on record, statistically. But the past 17 years – the so-called pause in global warming – are without a doubt the warmest period. And it's all down to the carbon. 

The colour of warming: NASA's video builds to a sunburst heat climax during the “pause years” of 1998–2014.

It’s official. 2014 was the warmest year on record for the surface of our great big, blue marble. Well, nominally it was the warmest. Statistically, not so much. 

That's the gist of a debate that has broken out – mostly in the nerdy reaches of the blogosphere – about the latest bellwether signal that global warming has no intention of taking a hike – of stopping or “pausing” – unless we press pause ourselves.

Early this year, all five of the major climate research groups and agencies that keep tabs on the planet's temps on land and sea, as well as the World Meteorological Organization, concurred that the average temperature anomaly (the deviation, up or down, from a reference baseline period) for 2014 was higher than any they had ever recorded. Only one, the UK's Met Office, declared 2014 a dead heat with 2010.

In contrast, both of the research groups that analyze the satellite record reported that 2014 was warm, but not record warm. For one group, the anomaly was third highest; for the other, a tepid 6th.

What every report had in common was that the slight difference between the top three warmest years – or the top six for the outlier satellite group – was smaller than the margin of error of roughly 5 to 10 hundredths of a degree.

In the United States, for example, the National Oceanic and Atmospheric Administration's (NOAA's) global temperature anomaly for 2014 of +0.69 degrees C. (using the entire 20th century as their baseline) was just 4 hundredths of a degree higher than their previous record: a tie between 2010 and 2005. And those years had beaten the blowout record set in 1998 (thanks to the hottest El Niño ever recorded) by just 2 hundredths of a degree.

When the margin of error for measuring things with 95% accuracy is larger than the difference between those things, statistically they're considered to be no different – “tied.” So, statistically, no climate scientist could or would declare any of the last few warmest years to be the warmest. Still, 2014 was the best candidate. Such was the fine print in most every report, and even in some of the news stories. 

At a press briefing this January, NASA and NOAA spelled out the odds that each of the closest contenders might truly be the warmest year on record. 2014 “won,” albeit with less than 50 percent confidence. 

With so many temperature records being set in recent years, it should come as no shock that all but one of the 15 warmest years on record (going back as far as 1850, but likely for thousands of years) have occurred during our fledgling century (beginning with 2001), according to most, if not all, of the temperature-keepers. The only exception was 1998 – the year of that killer El Niño.

The Warmest “Pause” 

You may have noticed that politicians and pundits who like to preface particularly perverse or head-in-the-sand declarations about climate change with “Now I’m not a scientist, but…” are very fond of the meme that there has been no warming for umpteen years – typically since 1998 or late 1997.  

Ironically, there is scientific method to their cherry-picking cleverness. 

If you look at a graph depicting global temperature – like the wavy red line in the one at the end of this piece – you'll notice that while the trend is clearly up, the path is a very erratic one. At times the underlying trend looks more like a staircase – flat tread, vertical riser – than a smooth slope. There's a reason for this: forces other than increasing atmospheric greenhouse gas concentrations (natural forces mostly, like El Niño and his chilly sister La Niña, major volcanic eruptions and continuous variations in solar intensity) are constantly buffetting the planet's temperature up and down. Over the medium term – since 1900, for example – they've done little more than cancel each other out, leaving the long-term trend of anthropogenic warming undisturbed. But while they're bashing it out in the short term, there are inevitable periods when they distort the warming trend so badly it looks like the planet is about to boil over or, conversely, slide into the next Ice Age (see for example 1945–1978).

A good example was the 1990s. When Mount Pinatubo erupted in the summer of 1991, the sunlight-dimming ash it spewed into the atmosphere took a whopping 0.5 degree bite out of the planet's temperature over the next couple years. A waning solar cycle added to the chill. Only a moderate EL Niño and the continuing rise in greenhouse gas concentrations countered the cooling. But toward the end of the 90s, nature did a flip-flop. That record El Niño of 1997 and 1998 transferred perhaps half as much heat from the Pacific to the atmosphere as Pinatubo had shut out in 1992 and 1993. The result was a truly apocalyptic (and statistically significant) warming trend from early 1992 thru late 1998 of approximately 7.5 degrees per century (using the land and ocean-based temperature records) or 10 degrees per century (using the satellite-based records). 

Late in 1998, had you graphed the warming trend since mid-1992 you could have sounded the (false) alarm that the planet is warming at a rate of over 10 degrees C. per century, even using the satellite record (above) of outspoken anthropogenic climate change doubters John Christy and Roy Spencer of the University of Alabama at Huntsville (UAH).

A clever climate change “alarmist” could have waved that cherry-picked factoid in the face of the doubting Thomases – perhaps created a cool infographic, had that been an option – and blinded them with pseudoscience. But it's the climate change deniers and obfuscators who have been playing that card lately, based on the same misleading effect. Their no-warming disinfographics typically start with the peak El Niño year of 1998, which dwarfed all previous heat records (no statistical uncertainty there). Their disinfographics end at the present date, which has been opportune for their purposes since the late 2000s when solar intensity and the El Niño/La Niña cycle began simultaneously trending cool. Their final cherry-picking flourish is to seek out whichever temperature record shows the least warming. Lately, the RSS satellite record has delivered the goods. 

But one thing even cherry-pickers can't find is anything close to a statistically significant cooling trend – not even with RSS. Statistically flat is as good as it gets. That's because (according to all but RSS) the warming trend has continued at a pace of about 0.6 to 1 degree per century since 1997/98. But because the trend is still inching its way back to statistical significance (95 percent or higher probability the trend is real, not random), it's scientifically acceptable to say “there has been no warming.” (You can verify these trends yourself at skepticalscience.com/trend.php.) 

But there’s more than one scientific way to answer the question “are we still warming?” 

After taking office in 2011, Florida governor Rick “I'm not a scientist” Scott prohibited the state's actual scientists and other civil servants from using the terms “global warming” and “climate change” in any of their communications.

A few issues back, I discussed how during the apparent “pause” or warming “hiatus” since 1998, heat has been accumulating, if anything, at an accelerating pace in other parts of the climate system: the oceans, which soak up over 90 percent of it, and the melting glaciers, ice sheets and sea ice. 

Still, if we insist on using the planet’s surface temperature as our only gauge for global warming, another tack is to do what the World Meteorological Organization does: compare the average annual surface temperature of consecutive time periods. The WMO does this every decade. Last time, it reported “the decadal rate of [temperature] increase between 1991–2000 and 2001–2010 was unprecedented.” The WMO's average global temperature figures popped from 14.26 degrees C. in the 1990s to 14.47 in the 2000s. If a seemingly pausey decade like the 2000s can raise the planet's temperature one fifth of a degree, the world could easily be on course (if we don't slow our emissions) for another degree of warming by the time Justin Bieber cashes his first pension cheque. We wouldn't want an enfeebled old Biebs to bear the brunt of our reckless emissions.

We can use the WMO's method to compare the “pause period” to the identical-length period that preceded it. Data from NOAA gives us an average annual temperature anomaly for 1998 thru 2014 (17 years) of +0.58 degrees C. It comes with a margin of error of just 0.03 degrees, meaning there is a 95% probability the anomaly is somewhere between +0.55 degrees and +0.61 degrees. In contrast, for 1981–1997 (17 years) the average anomaly is just +0.295 degrees, with a margin of error of 0.05 degrees. So the plateaulike heat wave of the pause years has been over a quarter of a degree warmer than the steep heat rise of the 17 years that preceded it. Not only is this a nominally substantive temperature difference, it's an extremely significant one. Even applying very conservative statistical methods, the odds are in the hundreds of millions to one that the 17-year “pause” has been warmer than the 17-year period that preceded it. And that makes it the warmest 17-year period since we began measuring global temperature over 150 years ago – and probably the warmest in thousands of years, based on proxy temperature records using tree rings, ice cores and other clues. 

(More precisely, with a mean temperature anomaly 0.285 degrees higher than the previous 17-year period [0.58 minus 0.295], the implicit warming rate during “the pause” has been 0.168 degrees per decade, or nearly 2 degrees per century.)

Not that evidence like this will deter the no-warming-since-record-hot-year crowd. They have a fallback position: it may still be warming, but it’s not us and never was. CO₂ isn’t the enemy; it's a plant food, don't ya know? ( CO₂ is a plant food, of course. It's also an agent of ecocide. In the oceans, carbonic acid derived from our excessive CO2 emissions is killing off coral reefs and shellfish, with potentially disastrous consequences.) Some, like the Alberta oil industry-based “Friends of Science,” insist the sun is doing most of whatever warming they’re willing to acknowledge. Others, like U.S. Senate Pseudoscience Czar James Inhofe, put it down to a natural cycle or the planet's spontaneous emergence from the Little Ice Age.

But climate scientists have identified no such natural explanations. What they have determined is that the only necessary and sufficient cause for modern global warming is humanity's escalating greenhouse gas emissions. This has been especially evident since those emissions began breaking bad in the 1950s, only to have their heating potential unleashed in the late 70s when cooling air pollutants, like soot and sulphur dioxide, that spew, like CO2, from smokestacks and tailpipes were capped by clean air laws. (Not that the sun has been an idle bystander. Climate scientists reckon a small increase in solar intensity did contribute slightly to the warming trend of the first half of the last century.) 

There’s a simple, infographic way to put this question of causality to a gut-check, the kind that might sway even a Bill O'Reilly or a Stephen Colbert (in character). The world’s longest directly measured record of atmospheric CO₂ began in 1958 at the Mauna Loa Observatory in Hawaii. The graph below shows what it looks like (it's the squiggly green line – squiggles are the seasons) plotted against NASA's surface temperature record (the wavy red line – it would end at a higher peak, but the data it's based on at WoodForTrees.org stops halfway through 2014), and the sunspot record which mirrors the cyclic fluctuations and longer-term trends in solar energy that floods our planet, albeit with less and less of it bouncing back into outer space thanks to the growing blanket of greenhouse gases that trap its heat down here (it's the wavy blue line). 

Take a look. 

You Belieber the judge.