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RE: Detailed evidence fails to support man-made climate change
Maury Siskel wrote:
-----Original Message-----
From: maury [mailto:maury@webtexas.com]
Sent: Monday, August 04, 2003 9:37 AM
To: John Jacobus
Cc: Radiation Safety; Mailing List for Risk Professionals; Kai Kaletsch
Subject: Re: Detailed evidence fails to support man-made climate change
<snip>
The consensus of atmospheric and climate scientists is that there is not
sufficient evidence and knowledge on which to base any policies so
drastic as the Kyoto Accord. They now also generally agree that none of
the four principal GCM's (general circulation models) are able to
provide an adequate basis for such policy decisions. Models do not help
either way as yet. And thus far, the balance of evidence appears to
support beneficial effects of increased atmospheric CO2. Many
dissertations lie between here and there .... <g>
__________
Actually, the consensus of atmospheric and climate scientists is pretty well represented by the IPCC Third Assessment Report. Probably the best quick source of information for technically literate readers is the Technical Summary of the TAR, an 82 page summary with pointers to the specific sections of the TAR providing the detailed treatment of each topic. All three volumes of the TAR and some supporting material are available on the IPCC web site <www.ipcc.ch>, freely downloadable as PDF files.
Some excerpts:
The global average surface temperature has increased by 0.6 +- 0.2 deg C since the late 19th Century.
The regional patterns of warming that occurred in the early part of the 20th Century were different than those that occurred in the latter part.
... diurnal temperature range is decreasing very widely, although not everywhere.
Surface, balloon, and satellite temperature measurements show that the troposphere and the Earth's surface have warmed and that the stratosphere has cooled. ... (Since 1979), the balloon and satellite records show significantly less lower-tropospheric warming than observed at the surface.
It is likely that the rate and duration of the warming of the 20th Century is larger than any other time during the last 1,000 years. The 1990s are likely to have been the warmest decade of the millennium in the Northern Hemisphere and 1998 is likely to have been the warmest year.
Since the time of the SAR [Second Assessment Report], annual land precipitation has continued to increase in the middle and high latitudes of the Northern Hemisphere (very likely to be 0.5 to 1.0%/decade), except over Eastern Asia.
It is likely that total atmospheric water vapour has increased several percent per decade over many regions of the Northern Hemisphere.
Decreasing snow cover and land-ice extent continue to be positively correlated with increasing land surface temperatures.
Northern Hemisphere sea-ice amounts are decreasing, but no significant trends in Antarctic sea-ice extent are apparent.
New data indicate that there likely has been an approximately 40% decline in Arctic sea-ice thickness in late summer to early autumn between the period of 1958 to 1976 and the mid-1990s and a substantially smaller decline in winter.
The behaviour of ENSO [El Nin~o - Southern Oscillation] ... has been unusual since the mid-1970s compared with the previous 100 years, with warm-phase ENSO episodes being relatively more frequent, persistent, and intense than the opposite cool phase.
New analyses show that in regions where total precipitation has increased, it is very likely that there have been even more pronounced increases in heavy and extreme precipitation events.
There is no compelling evidence to indicate that the characteristics of tropical and extratropical storms have changed.
Taken together, these trends illustrate a collective picture of a warming world.
... the atmospheric residence time of the greenhouse gas -- is a highly policy relevant characteristic. Namely, emissions of a greenhouse gas than has a long atmospheric residence time is a quasi-irreversible commitment to sustained radiative forcing over decades, century, and millennia, before natural processes can remove the quantities emitted.
The atmospheric concentration of CO2 has increased from 280 ppm in 1750 to 367 ppm in 1999. ... The rate of increase over the past century is unprecedented, at least during the past 20,000 years.
Process-based modelling (terrestrial and ocean carbon models) has allowed preliminary quantification of mechanisms in the global carbon cycle.
Atmospheric methane (CH4) concentrations have increased by about 150% (1060ppb) since 1750.
The atmospheric abundance of CH4 continues to increase from 1610 ppb in 1983 to 1745 ppb in 1998, but the observed annual increase has declined during this period.
Ozone (O3) is an important greenhouse gas present in both the stratosphere and troposphere.
The observed losses of stratospheric ozone layer over the past two decades have caused a negative forcing of 0.15 +- 0.1 W m^-2 (i.e., a tendency toward cooling) of the surface troposphere system.
The global average radiative forcing due to increases in tropospheric ozone since pre-industrial times is estimated to have enhanced the anthropogenic greenhouse gas forcing by 0.35 +- 0.2 W m^-2.
..., substantial progress has been achieved in better defining the direct effect of a wider set of different aerosols.
Estimates of the indirect radiative forcing by anthropogenic aerosols remain problematic, although observational evidence points to a negative aerosol-induce indirect forcing in warm clouds.
Changes in land use, deforestation being the major factor, appear to have produced a negative radiative forcing of -0.2 +- 0.2 W m^-2.
Radiative forcing of the climate system due to solar irradiance change is estimated to be 0.3 +- 0.2 W m^-2 for the period 1750 to the present ... and most of the change is estimated to have occurred during the first half of the 20th Century.
A major feedback accounting for the large warming predicted by climate models in response to an increase in CO2 is the increase in atmospheric water vapour.
Clouds represent a significant source of potential error in climate simulations.
Major improvements have taken place in modelling ocean processes, in particular heat transport. These improvements, in conjunction with an increase in resolution, have been important in reducing the need for flux adjustments in models and in producing realistic simulations of natural large-scale circulation patterns and improvements in simulating El Nin~o.
The representation of sea-ice processes continues to improve, with several climate models now incorporating physically-based treatments of ice dynamics. The representation of land-ice processes in global climate models remains rudimentary.
Research with models containing the latest representations of the land surface indicates that the direct effects of increased CO2 on the physiology of plants could lead to a relative reduction in evapotranspiration over the tropical continents, with associated regional warming and drying over that predicted for conventional greenhouse warming effects.
There is an increasing realization that natural circulation patterns, such as ENSO and NAO (North Atlantic Oscillation), play a fundamental role in global climate and its interannual and longer-term variability.
Climate change may manifest itself both as shifting means, as well as changing preference of specific climate regimes, as evidence by the observed trend toward positive values for the last 30 years in the NAO and the climate "shift" in the tropical Pacific about 1976.
The thermohaline circulation (THC) is responsible for the major part of the meridional heat transport in the Atlantic Ocean.
The possibility for rapid and irreversible changes in the climate system exists, but there is a large degree of uncertainty about the mechanisms involved and hence also about the likelihood or time-scales of such transitions.
Coupled models have evolved and improved significantly since the SAR. In general, they provide credible simulations of climate, at least down to sub-continental scales and over temporal scales from seasonal to decadal. Coupled models, as a class, are considered to be suitable tools to provide useful projections of future climates.
The warming of the last 100 years is very unlikely to be due to internal variability alone, as estimated by current models.
There is a wide range of evidence of qualitative consistencies between observed climate changes and model responses to anthropogenic forcing.
All simulations with greenhouse gases and sulphate aerosols that have been used in detections studies have found that a significant anthropogenic contribution is required to account for surface and tropospheric trends over at least the last 30 years.
Evidence of a human influence on climate is obtained over a substantially wider range of detection techniques.
It is very likely that the 20th Century warming has contributed significantly to the observed sea level rise, through thermal expansion of sea water and widespread loss of land ice.
Synopsis
In the light of new evidence and taking into account the remaining uncertainties, most of the observed warming over the last 50 years is likely to have been due to the increase in greenhouse gas concentrations.
Thus endeth excerpts from the TAR Technical Summary. I left out the TAR TS treatment of model-based projections of climate into the 21st Century. I encourage the reader to read both the Imhofe speech and the TAR TS and decide which is a scientific evaluation of the evidence and which is a Catechism, laying out the requirements of a faith.
The Imhofe floor speech is a farrago of mis-representations of arguments, climate observations, and the actual views of the climate experts that are cited, combined with a number of non sequiturs. For several of the experts, specific remarks are taken out of context, while the overall view of the expert is one of strong support for the hypothesis that human activity (greenhouse gases, land use changes, etc.) is having a demonstrable effect on the Earth's climate and will have a much stronger effect during this Century. Jerry Mahlman, Tom Wigley, and Tom Karl fall into this category. I have to go back and reread Freeman Dyson's review of Vaclav Smil's recent book, but I remember it more as a focus on remaining uncertainties and not agreement with the Climate Sceptic faith that 1) Climate is not warming, or 2) Well, if it is, it's not our fault, or 3) Well, if it is our fault, a warmer climate will actually be better for us.
Finally, regarding the much-ballyhooed disagreement between the Spencer/Christy satellite data and the surface temperature data, the reader can visit the Idso family anti-global-warming web site <www.co2science.com> and review the tropospheric temperature trends. In particular, for the Earth north of 20N latitude, where about 75% of the Earth's population lives, the satellite data shows a statistically significant warming trend (explaining 40.86% of the variation in the data) is 0.2259 deg C per decade over the last 24 years. The Idso's web site also has radiosonde data and two surface temperature data set, with an easy to use user interface. Highly recommended, although I would suggest taking the Idso editorial views with more than a few grains of salt.
A couple of other groups of scientists have independently analyzed the Spencer/Christy raw data, coming up with significantly different results and larger warming trends. My own view -- a product of reading the Spencer/Christy/et al. papers that explain how they turn oxygen atom GHz emissions into weighted, spatially averaged temperatures over 100,000 square km blocks of troposphere -- is that satellite "brightness temperatures" should be added to Bismarck's list of sausages and legislation as things that you should not watch being made.
Best regards.
Jim Dukelow
Pacific Northwest National Laboratory
Richland, WA
jim.dukelow@pnl.gov
These comments are mine and have not been reviewed and/or approved by my management or by the U.S. Department of Energy.
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