New paper finds negative-feedback cooling from water vapor could almost completely offset warming from CO2

A new paper published in the Journal of Geophysical Research Atmospheres finds water vapor can act as a negative-feedback cooling effect to significantly counteract anthropogenic global warming. 

According to the paper, "The satellite observations have shown that warming of the tropical Indian Ocean and tropical Western Pacific Ocean -- with resulting increased precipitation and water vapor there -- causes the opposite effect of cooling in the tropical tropopause region above the warming sea surface. Once the tropical tropopause cools, less water vapor is present in the tropical tropopause and also above in the stratosphere,

Since water vapor is a very strong greenhouse gas, this effect leads to a negative feedback on climate change. That is, the increase in water vapor due to enhanced evaporation from the warming oceans is confined to the near- surface area, while the stratosphere becomes drier. Hence, this effect may actually slightly weaken the more dire forecasted aspects of an increasing warming of our climate, the scientists say."

The paper itself says, "In the lower stratosphere, the changes in water vapor and temperature due to projected future sea surface temperatures are of similar strength to, though slightly weaker than, that due directly to projected future CO2, ozone, and methane," which would indicate that this negative-feedback cooling effect is almost equivalent to the warming effect of man-made CO2, ozone, and methane and could almost fully offset global warming. 

The paper is similar to another recent paper published in Nature Climate Change, finding warming of sea surface temperatures in the Indian and Pacific Ocean 'warm pool' is causing less water vapor to enter the top of the troposphere and could cause global cooling from this negative-feedback. The papers add to many others finding water vapor acts as a negative-feedback, not positive as assumed by IPCC climate models. Climate model false assumptions of positive-feedback from water vapor are the entire basis of Mann-made global warming alarm. 

Nature can, selectively, buffer human-caused global warming, say scientists

February 2, 2014

Summary:

Can naturally occurring processes selectively buffer the full brunt of global warming caused by greenhouse gas emissions resulting from human activities? Yes, says a group of researchers in a new study.


As the globe warms, ocean temperatures rise, leading to increased water vapor escaping into the atmosphere. Water vapor is the most important greenhouse gas, and its impact on climate is amplified in the stratosphere.

Can naturally occurring processes selectively buffer the full brunt of global warming caused by greenhouse gas emissions resulting from human activities?

Yes, find researchers from the Hebrew University of Jerusalem, Johns Hopkins University in the US and NASA's Goddard Space Flight Center.

As the globe warms, ocean temperatures rise, leading to increased water vapor escaping into the atmosphere. Water vapor is the most important greenhouse gas, and its impact on climate is amplified in the stratosphere.

In a detailed study, the researchers from the three institutions examined the causes of changes in the temperatures and water vapor in the tropical tropopause layer (TTL). The TTL is a critical region of our atmosphere with characteristics of both the troposphere below and the stratosphere above.

The TTL can have significant influences on both atmospheric chemistry and climate, as its temperature determines how much water vapor can enter the stratosphere. Therefore, understanding any changes in the temperature of the TTL and what might be causing them is an important scientific question of significant societal relevance, say the researchers.

The Israeli and US scientists used measurements from satellite observations and output from chemistry-climate models to understand recent temperature trends in the TTL. Temperature measurements show where significant changes have taken place since 1979.

The satellite observations have shown that warming of the tropical Indian Ocean and tropical Western Pacific Ocean -- with resulting increased precipitation and water vapor there -- causes the opposite effect of cooling in the TTL region above the warming sea surface. Once the TTL cools, less water vapor is present in the TTL and also above in the stratosphere,

Since water vapor is a very strong greenhouse gas, this effect leads to a negative feedback on climate change. That is, the increase in water vapor due to enhanced evaporation from the warming oceans is confined to the near- surface area, while the stratosphere becomes drier. Hence, this effect may actually slightly weaken the more dire forecasted aspects of an increasing warming of our climate, the scientists say.
The researchers are Dr. Chaim Garfinkel of the Fredy and Nadine Herrmann Institute of Earth Sciences at the Hebrew University and formerly of Johns Hopkins University, Dr. D. W. Waugh and Dr. L. Wang of Johns Hopkins, and Dr. L. D. Oman and Dr. M. M. Hurwitz of the Goddard Space Flight Center. Their findings have been published in theJournal of Geophysical Research: Atmospheres, and the research was also highlighted in Nature Climate Change.

Story Source:

The above story is based on materials provided by Hebrew University of Jerusalem.Note: Materials may be edited for content and length.

Journal Reference:
C. I. Garfinkel, D. W. Waugh, L. D. Oman, L. Wang, M. M. Hurwitz. Temperature trends in the tropical upper troposphere and lower stratosphere: Connections with sea surface temperatures and implications for water vapor and ozone. Journal of Geophysical Research: Atmospheres, 2013; 118 (17): 9658 DOI: 10.1002/jgrd.50772


Temperature trends in the tropical upper troposphere and lower stratosphere: Connections with sea surface temperatures and implications for water vapor and ozone

C. I. Garfinkel1,2,*, D. W. Waugh1, L. D. Oman3, L. Wang1, M. M. Hurwitz3,4

Satellite observations and chemistry-climate model experiments are used to understand the zonal structure of tropical lower stratospheric temperature, water vapor, and ozone trends. The warming in the tropical upper troposphere over the past 30 years is strongest near the Indo-Pacific warm pool, while the warming trend in the western and central Pacific is much weaker. In the lower stratosphere, these trends are reversed: the historical cooling trend is strongest over the Indo-Pacific warm pool and is weakest in the western and central Pacific. These zonal variations are stronger than the zonal-mean response in boreal winter. Targeted experiments with a chemistry-climate model are used to demonstrate that sea surface temperature (hereafter SST) trends are driving the zonal asymmetry in upper tropospheric and lower stratospheric tropical temperature trends. Warming SSTs in the Indian Ocean and in the warm pool region have led to enhanced moist heating in the upper troposphere, and in turn to a Gill-like response that extends into the lower stratosphere. The anomalous circulation has led to zonal structure in the ozone and water vapor trends near the tropopause, and subsequently to less water vapor entering the stratosphere. The radiative impact of these changes in trace gases is smaller than the direct impact of the moist heating. Projected future SSTs appear to drive a temperature and water vapor response whose zonal structure is similar to the historical response. In the lower stratosphere, the changes in water vapor and temperature due to projected future SSTs are of similar strength to, though slightly weaker than, that due directly to projected future CO2, ozone, and methane.