Ocean climate assessments
The purpose of BALTEX Assessment of Climate Change for the Baltic Sea Basin (BACC) is to provide the scientific community with an assessment of ongoing climate change in the Baltic Sea basin. An important element is the comparison with the historical past (until about 1800) to provide a framework for the severity and unusualness of the change. Also changes in relevant environmental systems, due to climate change are assessed- such as hydrological change and land and water ecosystem changes. The results are now published (BACC Author Group, 2008) and the book presents the first comprehensive survey of past, present and possible future climate change in the region. In the past century there has been a marked increase of air temperature of more than 0.7 oC. This increase is after the “Little Ice Age” ended about 1880. Consistent with this increase in mean and extreme temperatures, other variables show changes, such as increase of winter runoff, shorter sea ice seasons and reduced ice thickness on rivers and lakes in many areas. No robust link to anthropogenic warming, which on the hemispheric scale has been causally related to increased levels of greenhouse gases in the atmosphere in “detection and attribution” studies, has been established. However, the identified trends in temperature and related variables are consistent with regional climate change scenarios prepared with climate models. Therefore, it is plausible that at least part of the recent warming in the Baltic Sea basin is related to the steadily increasing atmospheric concentrations of greenhouse gases. The situation is much less clear regarding precipitation.
For the future, the air temperature in the Baltic Sea basin could rise up to five degrees Celsius from now to 2100. Intensified winter precipitation may emerge later in this century over the entire area, while summers may become drier in the southern part – but this expectation is uncertain for the time being. Similarly, no clear signals, whether for the past or for the scenarios, are available with regard to change in wind conditions.
The project’s findings have also served as the basis of a report published by the Baltic Marine Environment Protection Commission (HELCOM, 2007). A second BACC climate report is planned to 2012. Detailed information will be available on the BALTEX/BACC website.
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