A new study finds that when climate models factor in the temporary warming and cooling impact of El Niño and La Niña, they accurately predict recent global warming. And that is consistent with recent studies that led one climatologist to say, “Global temperatures look set to rise rapidly.”
GLOBAL WARMING CONTINUES TO ACCELERATE
A study last year found that global warming has accelerated in the past 15 years, especially in the ocean. As scientists had predicted, 90 percent of that warming ended up in the oceans. And we reported that Greenland’s ice melt increased five-fold since the mid-1990s. Another study that month found “sea level rising 60% faster than projected.”
And yet much of the media believes climate change isn’t what gets measured and reported by scientists, but is somehow a dialectic or a debate between scientists and deniers. So while 2010 was the hottest year on record and the 2000s the hottest decade on record, even prestigious media outlets like the New York Times keep pushing the meme that global warming has paused or inexplicably slowed down a great deal.
Back in December, researchers Cowtan and Way showed that much of the supposed slow down was due to missing data. As RealClimate explained in its post “Global Warming Since 1997 Underestimated by Half”:
A new study by British and Canadian researchers shows that the global temperature rise of the past 15 years has been greatly underestimated. The reason is the data gaps in the weather station network, especially in the Arctic. If you fill these data gaps using satellite measurements, the warming trend is more than doubled in the widely used HadCRUT4 data, and the much-discussed “warming pause” has virtually disappeared.
“There are no permanent weather stations in the Arctic Ocean, the place on Earth that has been warming fastest,” as New Scientist explained five years ago. “The UK’s Hadley Centre record simply excludes this area, whereas the NASA version assumes its surface temperature is the same as that of the nearest land-based stations.” As I’ve discussed many times, that’s why we know with high certainty that the planet has actually warmed up more in the past decade than reported by the global temperature records, especially the Hadley Center’s.
So there’s no “pause” in global warming, even for surface air temperatures. At that point, the remaining question was, why have surface temperatures slowed their growth, when ocean temperatures and glaciers and Arctic sea ice — which is where 95% of global warming ends up — have seen accelerated warming?
In February, new research offered an answer to that question. It found that the slowdown in the rate of surface warming is because trade winds have sped up in an unprecedented fashion, mixing more heat deeper into the oceans, while bringing cooler water up to the surface. Since more than 90 percent of human-induced planetary warming goes into the oceans, while only 2 percent goes into the atmosphere, small changes in ocean uptake can have huge impact on surface temperatures.
Lead author Prof. Matthew England explained in a news release:
“Scientists have long suspected that extra ocean heat uptake has slowed the rise of global average temperatures, but the mechanism behind the hiatus remained unclear…. But the heat uptake is by no means permanent: when the trade wind strength returns to normal –- as it inevitably will –- our research suggests heat will quickly accumulate in the atmosphere. So global temperatures look set to rise rapidly out of the hiatus, returning to the levels projected within as little as a decade.”
What that study found is that temperatures are likely to jump in the coming years since “the net effect of these anomalous winds is a cooling in the 2012 global average surface air temperature of 0.1–0.2°C.”
NEW STUDY VINDICATES CLIMATE MODELS
And that brings us to the new study published in Nature Climate Change, “Well-estimated global surface warming in climate projections selected for ENSO phase.” The El Niño-Southern oscillation (ENSO) is the cyclical warming and cooling of the central and eastern tropical Pacific, whose best known manifestations are El Niño and La Niña.
As the NASA chart at the top shows, over the short term ENSO can have a significant impact on global temperatures — and so it can impact the ability of even the latest climate models (so-called CMIP5 models) to accurately project temperatures over a period of 15 years or less.
In their abstract, the authors explain “Some studies and the IPCC Fifth Assessment Report suggest that the recent 15-year period (1998–2012) provides evidence that models are overestimating current temperature evolution.” But the authors note, “Such comparisons are not evidence against model trends because they represent only one realization where the decadal natural variability component of the model climate is generally not in phase with observations.”
The authors employed a clever way to figure out if the models were accurate or not. They took a great many simulations from 18 CMIP5 models. Then, as the UK Guardian explained, “looked at each 15-year period since the 1950s, and compared how accurately each model simulation had represented El Niño and La Niña conditions during those 15 years” – using the temperature trend in the Niño3.4 region, the key ENSO indicator.
In their study, the authors “present a more appropriate test of models where only those models with natural variability” that is “largely in phase with [ENSO] observations are selected from multi-model ensembles for comparison with observations. These tests show that climate models have provided good estimates of 15-year trends, including for recent periods and for Pacific spatial trend patterns.”
As the Guardian explains, “The study authors compared the simulations that were correctly synchronized with the ocean cycles (blue data in the left frame below) and the most out-of-sync (grey data in the right frame) to the observed global surface temperature changes (red) for each 15-year period” (using the corrected global temperature data from Cowtan and Way).
Thus, the recent faux pause in the rise of surface air temperatures turns out to be nothing more than a modest slowdown driven by the short-term ENSO trend, which has favored the cooler La Niñas in the last few years (as the NASA figure at the top shows). As the Guardian points out, this conclusion “is supported by many recent studies finding that unprecedentedly strong Pacific trade winds have been churning the ocean and funneling more heat to the deeper layers, leaving less to warm the surface. All signs point to this being a temporary change, and once the oceans begin to switch back to more frequent El Niño conditions, we expect to see less efficient ocean heat absorption leading to accelerated warming of global surface temperatures.”
Finally, since the new study reconfirms that the latest climate models are indeed accurate (once ENSO is taken into account), that means if we continue on our path of general inaction on climate change, we face “9°F Warming For U.S., Faster Sea Rise, More Extreme Weather, Permafrost Collapse.” The time to act is now.