Several fascinating new scientific papers have appeared recently that come to some very different conclusions about the trend in global average temperature and what causes it. One concludes that fluctuations in the El Nino explain the current 15-year "pause" in warming and cut future increases in man-made warming in half; a second finds that once missing data are taken into account there has been NO pause in warming at all; and a third reports that natural fluctuations in the Arctic explain the "pause" which could last until 2030.
So first, in a new article in the Asia-Pacific Journal of Atmospheric Science, University of Alabama in Huntsville researchers Roy Spencer and Danny Braswell use climate models to take into account the effects that natural variations in the El Nino Southern Oscillation (ENSO) has on global average temperature trends over the past 50 years. The ENSO is a phenomenon in which the surface temperatures over the southern Pacific Ocean fluctuate between hot and cold phases. According to Phys.org, they found:
The results suggest that these natural climate cycles change the total amount of energy received from the sun, providing a natural warming and cooling mechanism of the surface and the deep ocean on multi-decadal time scales.
"As a result, because as much as 50 percent of the warming since the 1970s could be attributed to stronger El Niño activity, it suggests that the climate system is only about half as sensitive to increasing CO2 as previously believed," Spencer said.
"Basically, previously it was believed that if we doubled the CO2 in the atmosphere, sea surface temperatures would warm about 2.5 C," Spencer said. That's 4.5° F. "But when we factor in the ENSO warming, we see only a 1.3 C (about 2.3° F) final total warming after the climate system has adjusted to having twice as much CO2." …
Spencer said it is reasonable to suspect that the increased La Niña cooling might be largely responsible for an ongoing "pause" in global warming that has lasted more than a decade. If that is the case, weak warming might be expected to revive when this phase of the El Niño-La Niña cycle shifts back to a warmer El Niño period.
In contrast, climate catastrophists cite as evidence that things are worse than they thought a new study in The Quarterly Journal of the Royal Meteorological Society by Kevin Cowtan from the University of York and Robert Way from the University of Ottawa (who both also contribute to the climate science website Skeptical Science). The two researchers apply some fancy statistical jiggering to climate temperature data from the Hadley Centre in the United Kingdom in an effort to figure out what is going on in the regions of the globe not well-covered by that dataset. They report:
The widely quoted trend since 1997 in the hybrid global reconstruction is two and a half times greater than the corresponding trend in the coverage-biased HadCRUT4 data. Coverage bias causes a cool bias in recent temperatures relative to the late 1990s which increases from around 1998 to the present. Trends starting in 1997 or 1998 are particularly biased with respect to the global trend. The issue is exacerbated by the strong El Niño event of 1997-1998, which also tends to suppress trends starting during those years.
The Guardian reports that the upshot of their new analysis is:
Both of their new surface temperature data sets show significantly more warming over the past 16 years than HadCRUT4. This is mainly due to HadCRUT4 missing accelerated Arctic warming, especially since 1997.
Cowtan & Way investigate the claim of a global surface warming 'pause' over the past 16 years by examining the trends from 1997 through 2012. While HadCRUT4 only estimates the surface warming trend at 0.046°C per decade during that time, and NASA puts it at 0.080°C per decade, the new kriging and hybrid data sets estimate the trend during this time at 0.11 and 0.12°C per decade, respectively.
In other words, there is no 15-year pause in global warming has all of the current datasets measuring global average temperature have reported.
And to make things even more "settled," there is a new study in Climate Dynamics by Georgia Tech climatologist Judith Currry and her colleague Marcia Wyatt that looks at temperature fluctuations in the Arctic region and finds that they are driven by natural "stadium wave" fluctuations produced by the Atlantic Multidecadal Oscillation (AMO) and sea ice extent in the Eurasian Arctic shelf seas. As Newswise reports the …
…'stadium-wave' signal that propagates like the cheer at sporting events whereby sections of sports fans seated in a stadium stand and sit as a 'wave' propagates through the audience. In like manner, the 'stadium wave' climate signal propagates across the Northern Hemisphere through a network of ocean, ice, and atmospheric circulation regimes that self-organize into a collective tempo.
The stadium wave hypothesis provides a plausible explanation for the hiatus in warming and helps explain why climate models did not predict this hiatus. Further, the new hypothesis suggests how long the hiatus might last…
"The stadium wave signal predicts that the current pause in global warming could extend into the 2030s," said Wyatt,…
Curry added, "This prediction is in contrast to the recently released IPCC AR5 Report that projects an imminent resumption of the warming, likely to be in the range of a 0.3 to 0.7 degree Celsius rise in global mean surface temperature from 2016 to 2035." …
How external forcing projects onto the stadium wave, and whether it influences signal tempo or affects timing or magnitude of regime shifts, is unknown and requires further investigation," Wyatt said. "While the results of this study appear to have implications regarding the hiatus in warming, the stadium wave signal does not support or refute anthropogenic global warming.
Interestingly, the study by Cowtan and Way suggesting that man-made global warming is continuing apace seems to be getting much more media attention than are the two suggesting explanations for why warming has paused and why it might not increase disastrously in the future. Curious.
Heads up: I will be sending in daily dispatches all next week from the 19th Conference of the Parties of the United Nations Framework Convention on Climate Change meeting in Warsaw.