A central variable in their models is sheer guesswork
Predicting how clouds will form in a warmer world remains a haze in a UN climate report due on Friday, affecting projected rises in temperatures and sea levels, scientists say. The UN climate panel, an authoritative group on global warming numbering 2,500 experts, is set to give its strongest warning yet that human activities are heating the planet and that warming may cause huge damage to nature by 2100.
A draft report has plugged many gaps since a last report in 2001, such as anomalies between temperatures measured by satellites or at the earth's surface or how far tiny, glinting particles of air pollution reflect sunlight back into space. But cloud formation in the 21st century -- hard enough for weather forecasters to predict for tomorrow -- is among the remaining puzzles. "Large uncertainties remain about how clouds might respond to global climate change," according to a draft of the report under review by the Intergovernmental Panel on Climate Change (IPCC), meeting in Paris. Warmer air can absorb more moisture, meaning more clouds and so more rain and snow in many regions. But much more cloud cover might also brake warming because more sunlight will bounce off the white tops back into space.
The report, the first of four on global climate this year by the IPCC, is due to be issued on Friday and will guide governments trying to work out policies to brake warming. The report says more water vapour will bring more rains and snow to many regions towards the poles, such as northern Europe, Canada, the northeast United States and the Arctic. In winter, precipitation would also increase in northern Asia and the Tibetan plateau, it says.
By contrast, rains are likely to decrease in many subtropical regions. And parts of Africa and Europe around the Mediterranean are likely to get drier, and winter rains would decrease in southwestern Australia, it says. In many regions, downpours will be more intense.
More snows could also offset any thaw of the vast Antarctic ice cap and the smaller cap on Greenland. If both melted over thousands of years world sea levels would be about 65 metres (around 215 ft) higher than today. "In a warmer climate, models suggest that the ice sheets could accumulate more snowfall, tending to lower sea level," the draft says. But it adds that rapid thawing at the fringes has probably outweighed any such trend in recent years. "In the interior of Greenland, the ice has been thickening," said Catherine Myrmehl, of the Nansen Environmental and Remote Sensing Center in Norway, based upon satellite readings. Many scientists reckon Greenland is losing ice overall.
The IPCC is likely to predict a "best estimate" of a temperature rise of 3 Celsius (5.4 Fahrenheit) by 2100 over pre-industrial times. And it is set to predict sea level rises this century of between 28 and 43 cms (11-17 inches), a lower band than forecast in the 2001 report.
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IS THE ANTARCTIC ICE SHEET SHRINKING OR GROWING OVERALL?
Discussing: Remy, F. and Frezzotti, M. 2006. "Antarctica ice sheet mass balance". Comptes Rendus Geoscience 338: 1084-1097.
Background
The authors note that "each year, about 2200 gigatonnes of snow fall on the Antarctic ice sheet and sink toward deeper layers, where it slowly changes into ice," which ice "then flows toward the coast, where the same quantity of ice is rejected to the ocean much later," noting further that "this annual balance corresponds to 6.5 mm of sea level, so that a slight imbalance may have an impact on sea-level change."
What was done
To get a better feel for the current status of the mass balance the Antarctic Ice Sheet and what we might expect to occur in the near and far future, Remy and Frezzotti reviewed "the results given by three different ways of estimating mass balance, first by measuring the difference between mass input and output, second by monitoring the changing geometry of the continent, and third by modeling both the dynamic and climatic evolution of the continent."
What was learned
Quoting the conclusions of the two researchers, "the East Antarctica ice sheet is nowadays more or less in balance, while the West Antarctica ice sheet exhibits some changes likely to be related to climate change and is in negative balance." In addition, they report that "the current response of the Antarctica ice sheet is dominated by the background trend due to the retreat of the grounding line, leading to a sea-level rise of 0.4 mm/yr over the short-time scale," which they describe in terms of centuries. However, they note that "later, the precipitation increase will counterbalance this residual signal, leading to a thickening of the ice sheet and thus a decrease in sea level."
What it means
Although there is a potential for short-term climatic fluctuations to either increase or decrease the water equivalent of the Antarctic ice sheet and, thereby, correspondingly impact global sea level, there is as yet no conclusive evidence that the huge ice sheet covering East Antarctica is being affected to any significant degree, especially in the way suggested by climate alarmists, i.e., excessive mass loss that raises sea level. Recent analyses of global sea level trends also support this conclusion (Jevrejeva et al., 2006; Holgate, 2007). In fact, they suggest there may well have been a slight decrease in the rate-of-rise of the world's oceans over the 20th century, possibly indicating a net positive Antarctic ice sheet mass balance over this period.
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A SIGNIFICANT "HOLE" IN "UNPRECEDENTED" 20TH-CENTURY GLOBAL WARMING
Discussing: Kunkel, K.E., Liang, X.-Z., Zhu, J. and Lin, Y. 2006. "Can CGCMs simulate the twentieth-century "warming hole" in the central United States?" Journal of Climate 19: 4137-4153.
Background
Citing the work of Folland et al. (2001), Robinson et al. (2002) and Pan et al. (2004), the authors note there was a lack of warming throughout the central and southeastern United States over the course of the 20th century, which phenomenon was dubbed a "warming hole" by the latter set of investigators.
What was done
For an area they denote the Central United States (CUS), which they describe as "one of the most agriculturally productive regions of the world and roughly defined around what is known as the 'Corn Belt'," Kunkel et al. used a data set of 252 surface climate stations with less than 10% missing temperature data over the period 1901-1999 to construct the CUS temperature time series plotted in the figure below, where mean global temperature as determined by Hansen et al. (2001) is also plotted. Then, for comparative purposes, they examined 55 coupled general circulation model (CGCM) simulations driven by "modern estimates of time-varying forcing," plus 19 pre-industrial unforced simulations, all derived from 18 CGCMs.
What was learned
It is obvious, as shown in the figure above, that the Central US 20th-century temperature series is vastly different from that of the globe as a whole, at least as it is represented by Hansen et al. In fact, rather than the final temperature of the 20th century being unprecedented over the past two millennia, as climate alarmists typically claim, the final 20th-century temperature of the Central US was more than 0.7 degrees cooler than it was a mere 65 years earlier. In addition, Kunkel et al. report that "the warming hole is not [our italics] a robust response of contemporary CGCMs to the estimated external forcings."
What it means
In the words of the researchers who conducted the study, "the warming hole indicates that anthropogenic forcing of the climate system can be accompanied by a regional temperature response different than expected," which fact "has important implications for impacts assessments." Indeed, it suggests that such model-based assessments can be radically wrong. It is also of interest to note that "during the period of most significant greenhouse gas buildup over the past century, i.e., 1930 and onward" - as we repeat issue after issue in our Temperature Record of the Week feature - the bulk of the United States, whose 20th-century CO2 emissions exceeded those of all other nations, experienced no net warming. Pesky!
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TWO NEW BOOKS CLAIM THAT GLOBAL WARMING IS NATURAL, MODERATE
Two powerful new books say today's global warming is due not to human activity but primarily to a long, moderate solar-linked cycle. Unstoppable Global Warming Every 1500 Years, by physicist Fred Singer and economist Dennis Avery was released just before Christmas. The Chilling Stars: A New Theory of Climate Change, by Danish physicist Henrik Svensmark and former BBC science writer Nigel Calder (Icon Books), is due out in March.
Singer and Avery note that most of the earth's recent warming occurred before 1940, and thus before much human-emitted CO2. Moreover, physical evidence shows 600 moderate warmings in the earth's last million years. The evidence ranges from ancient Nile flood records, Chinese court documents and Roman wine grapes to modern spectral analysis of polar ice cores, deep seabed sediments, and layered cave stalagmites.
Unstoppable Global Warming shows the earth's temperatures following variations in solar intensity through centuries of sunspot records, and finds cycles of sun-linked isotopes in ice and tree rings. The book cites the work of Svensmark, who says cosmic rays vary the earth's temperatures by creating more or fewer of the low, wet clouds that cool the earth. It notes that global climate models can't accurately register cloud effects.
The Chilling Stars relates how Svensmark's team mimicked the chemistry of earth's atmosphere, by putting realistic mixtures of atmospheric gases into a large reaction chamber, with ultraviolet light as a stand-in for the sun. When they turned on the UV, microscopic droplets -- cloud seeds -- started floating through the chamber. "We were amazed by the speed and efficiency with which the electrons [generated by cosmic rays] do their work of creating the building blocks for the cloud condensation nuclei," says Svensmark.
The Chilling Stars documents how cosmic rays amplify small changes in the sun's irradiance fourfold, creating 1-2 degree C cycles in earth's temperatures: Cosmic rays continually slam into the earth's atmosphere from outer space, creating ion clusters that become seeds for small droplets of water and sulfuric acid. The droplets then form the low, wet clouds that reflect solar energy back into space. When the sun is more active, it shields the earth from some of the rays, clouds wane, and the planet warms.
Unstoppable Global Warming documents the reality of a moderate, natural, 1500-year climate cycle on the earth. The Chilling Stars explains the why and how.
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Many people would like to be kind to others so Leftists exploit that with their nonsense about equality. Most people want a clean, green environment so Greenies exploit that by inventing all sorts of far-fetched threats to the environment. But for both, the real motive is generally to promote themselves as wiser and better than everyone else, truth regardless.
Global warming has taken the place of Communism as an absurdity that "liberals" will defend to the death regardless of the evidence showing its folly. Evidence never has mattered to real Leftists
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Jim Hansen and his twin
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