February 1, 2010

What’s Happened to Global Warming?

One of the enduring pillars of the climate change issue is that the temperature of the Earth is increasing at an unprecedented rate … we’ve heard it a million times over the past few decades. However, it is well known that the temperature of the Earth has not increased over the past decade, and the lack of recent warming is now receiving serious consideration in the leading scientific journals. Two recent articles are of particular interest to us at World Climate Report.

The first was published in Geophysical Research Letters by two scientists with the National Climatic Data Center in North Carolina and Lawrence Berkeley National Laboratory in California. The article is entitled “Is the climate warming or cooling?” which must send shivers up the spines of the many folks in the global warming alarmist camp. We are now in 2010, and an article is published in a leading journal questioning whether or not the climate is warming or cooling? Go figure.

Easterling and Wehner begin their piece noting that “Anthropogenic climate change is one of the most contentious scientific issues of our time. Not surprisingly the issue has generated numerous blogs and websites with a wide range of views on the subject. According to a number of these sources the climate is no longer warming, in fact, some claim the planet has been “cooling’’ since 1998”. They immediately admit that “It is true that if we fit a linear trend line to the annual global land-ocean surface air temperature” “for the period 1998 to 2008 there is no real trend”. Correct – the satellite-based, balloon-based, and thermometer-based global temperature records show no warming whatsoever over the past decade. Claims that the Earth’s temperature is rising at an unprecedented rate are clearly false – nothing could be further from reality.

We fully understand that the climate system produces substantial natural variation and even with a robust upward trend, there will be periods of no trend or even cooling. Easterling and Wehner examine historical temperature trends over past decades and model predictions over coming decades, and they conclude “Therefore, it is reasonable to expect that the natural variability of the real climate system can and likely will produce multi-year periods of sustained ‘‘cooling’’ or at least periods with no real trend even in the presence of long-term anthropogenic forced warming. Claims that global warming is not occurring that are derived from a cooling observed over such short time periods ignore this natural variability and are misleading.”

We agree – expecting a monotonic increase in global temperatures is inconsistent with historical temperature records, model predictions, and our general understanding of the climate system. Easterling and Wehner basically show that with little-to-no external forcing of global climate, we will still get decades of warming and cooling. They note that no real cause is needed to produce a decade of cooling – it is all just part of the natural variability of climate. Fair enough.

However, a bombshell article just appeared in the literature providing a possible physical explanation of why the temperature of the Earth flattened out over the past decade. The article also highlights serious deficiencies in the climate models that are expected to provide predictions of climate change in the coming decades.

The article will appear in Science (it is available via Sciencexpress) and was generated by scientists with the NOAA Earth System Research Laboratory and the Cooperative Institute for Research in Environmental Sciences in Colorado and the Physics Institute in Bern, Switzerland. These are hardly groups associated with any high level of climate change skepticism, and we could only imagine how the scientists are being treated currently by the colleagues … we applaud their courage.

Solomon et al. begin their article stating “Over the past century, global average surface temperatures have warmed by about 0.75°C. Much of the warming occurred in the last half century, over which the average decadal rate of change was about 0.13°C, largely due to anthropogenic increases in well-mixed greenhouse gases. However, the trend in global surface temperatures has been nearly flat since the late 1990s despite continuing increases in the forcing due to the sum of the well-mixed greenhouse gases (CO2, CH4, halocarbons, and N2O), raising questions regarding the understanding of forced climate change, its drivers, the parameters that define natural internal variability, and how fully these terms are represented in climate models.”

Admitting that the trend in global temperatures has been flat over the past decade will not win any awards for this team, so we once again applaud their honesty. The team suggests that part of the reason for the flatness deals with the amount of water high-up in the upper troposphere, the tropopause, and the lower stratosphere. They clearly state “Water vapor is a highly variable gas. Tropospheric water vapor increases in close association with warming and this represents a major climate feedback that is well simulated in global climate models. In sharp contrast, current global models are limited in their representations of key processes that control the distribution and variability of water within the stratosphere”. Furthermore they note “Current global climate models simulate lower stratospheric temperature trends poorly and even up-to-date stratospheric chemistry-climate models do not consistently reproduce tropical tropopause minimum temperatures or recently observed changes in stratospheric water vapor.”

We agree – climate models are terrific constructs of our time, but they do not include many of the potentially important processes that control the global climate system. Solomon et al. provide convincing arguments that stratospheric water vapor levels have a significant impact on global temperatures, and they reveal that recent measurements since 2000 show “strong evidence for a sharp and persistent drop of about 0.4 parts per million by volume (ppmv) after the year 2000. Observations of lower stratospheric tropical ozone changes also reveal a sharp change after 2000”. For whatever reason, the stratosphere has been losing water vapor, and Solomon et al. reveal that this trend should put the brakes on any global temperature increase. They state that “the decline in stratospheric water vapor after 2000 should be expected to have significantly contributed to the flattening of the global warming trend in the past decade, and stratospheric water increases may also have acted to steepen the observed warming trend in the 1990s.”

The article is full of comments about how poorly the climate models represent key features in the Earth-atmosphere system, particularly when dealing with important processes above the troposphere. This flattening of the Earth’s temperature must be very inconvenient for the global warming alarmists, and we suspect many more articles on the subject will be appearing in the literature throughout 2010 … stay tuned!

References:

Easterling, D. R., and M. F. Wehner. 2009. Is the climate warming or cooling? Geophysical Research Letters, 36, L08706, doi:10.1029/2009GL037810.

Solomon, S., K. Rosenlof, R. Portmann, J. Daniel, S. Davis, T. Sanford, G.-K. Plattner. 2010. Contributions of stratospheric water vapor to decadal changes in the rate of global warming. Sciencexpress. www.sciencexpress.org / 28 January 2010 / Page 1 / 10.1126/science.1182488.




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