We're picking up speed
The new final report of the UNO climate panel will present alarming figures and forecasts on the global warming on Friday. The latest data, meanwhile, confirm - and even exceed - the trends predicted five years ago.
There will probably only be a softened version when the 500 participating climatologists, biologists, geoscientists and oceanologists from all over the world have put their findings into words together with government representatives from a hundred countries. After all, oil exporters, booming emerging countries and the skeptical remnants of the Bush administration who are still in office have little interest in allowing overly drastic statements about climate change – after all, calls for more consistent savings measures could finally get the upper hand and reduce lucrative business.
Nevertheless, the new final report of the Intergovernmental Panel on Climate Change (IPCC) of the United Nations is much sharper and more frightening than its previous version from 2001. At least that is what a report in the Süddeutsche Zeitung says, which already published the final version in advance of the scientific chapter is available. Accordingly, this summary of the knowledge determined in recent years confirms that humans are now undoubtedly the cause of climate change. The increase in greenhouse gases in the earth's atmosphere since 1750 is mainly due to the burning of oil, gas and coal as well as modern agriculture with slash and burn, improper land use and over-fertilization. They would have five times the impact on global warming as fluctuations in solar radiation.
The consequences can be seen worldwide: Eleven of the twelve warmest years since climate records began around 1850 were in the period between 1994 and 2005. In the seas, a general increase in temperature can be detected down to a depth of 3000 meters, their levels are currently rising more than three millimeters per year. In the mountains, the Arctic and parts of the Antarctic, the glaciers are melting faster and faster – in 2005 alone they lost an average of sixty centimeters in thickness in the Alps and Andes or in the Himalayas, while in Greenland around 100 gigatonnes are melting every year. Extreme weather events such as droughts, heat waves or heavy rainfall are increasing worldwide, and even the increasing intensity of hurricanes could be attributed to global warming. And all trends should accelerate in the future.
A few skeptics – who are almost non-existent in science any more on the subject of climate change – usually object at this point that these forecasts are only computer calculations that do not reflect reality due to insufficient amounts of data and misunderstood relationships. As has often been shown before, the opposite is also the case here, as a new analysis by scientists led by Stefan Rahmstorf from the Potsdam Institute for Climate Impact Research testifies [1].
They compared the actually measured carbon dioxide values in the atmosphere, the development of average global temperatures and the changes in sea levels over the last five years with forecasts from the year 2001, which appeared in the IPCC report at the time. The scenarios presented there begin again with their recording in 1990, but model calculations and the observed climate data remain independent of each other: The long-term simulations are based on physical parameters and are not compared, for example to reflect the most recent temperatures, says Rahmstorf. Also, in the early 1990s, global aggregated sea level figures were not available.
And indeed, the IPCC projections reflect the global increase in CO2 almost congruently. Back then, the computers calculated a value of just over 380 ppm (parts per million) for the year 2005; today it is just above this mark – with accelerated growth since the turn of the millennium. The real development of average temperatures also follows the model calculations. They have increased by 0.33 degrees Celsius over the past 16 years, which is even the upper limit of the warming considered possible by the IPCC.
However, it is still unclear to the scientists why the planetary fever curve is already ahead of the degree of pollution during the short period of comparison - especially because the atmospheric plus of other heat-increasing greenhouse gases such as methane, nitrogen oxides and CFC lags behind the IPCC estimates. A higher internal variability in the climate system or a weaker influence of aerosols, which act like a kind of dirty parasol and have a cooling effect, could be assumed. However, it is possible that carbon dioxide reacts more sensitively and retains more thermal radiation in the atmosphere, so that its effect has so far been underestimated.
With the increase in global water levels, however, the projection is noticeably lagging behind reality, as shown by large-scale reconstructed and evaluated data from gauge recordings and figures obtained from satellite altimetry from 1993 onwards. While the IPCC report at the time only assumed less than 2 millimeters per year, satellites and gauges each measured more than 3 millimeters - an expression of the accelerated glacier melt in the Arctic and above all the expanding warmer water. The growth rates of the last twenty years are also a quarter higher than in all previous intervals of the same length since 1890.
Here, too, the scientists point out that intra-oceanic fluctuations - which can extend over decades - distort the current status somewhat: the levels do not necessarily have to continue to rise at this comparatively extreme rate in the future; the seas could also advance a little more slowly towards the coasts. Rahmstorf, his colleagues and the IPCC experts meeting in Paris are certain that carbon dioxide concentration, temperatures and water levels will continue to rise and that the corresponding negative consequences will set in – despite all the political and economic influences.
