Fortunately, the Second World Climate Conference in 1990 requested in its ministerial part a United Nations Convention on Climate Change to be ready for the Earth Summit (United Nations Conference on Environment and Development, UNCED) in Rio de Janeiro. Its official title at signature by 153 heads of States in June 1992 became: United Nations Framework Convention on Climate Change (UNFCCC), indicating that other legal instruments would be needed.
UNFCCC has a central goal in its paragraph 2: The ultimate objective of this Convention and any related legal instruments that the Conference of the Parties may adopt is to achieve, in accordance with the relevant provisions of the Convention, stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous interference with the climate system. Such a level should be achieved within a time-frame sufficient to allow ecosystems to adapt naturally to climate change, to ensure that food production is not threatened and to enable economic development to proceed in a sustainable manner.
Its implementation is the task of a century, because the time-scales of climate system components reach centuries and even millennia and any clearly visible impact of measures taken now on climate variables will only be seen after several decades. The three side-conditions under which stabilization of greenhouse gas concentrations in the atmosphere has to be reached are not yet fully understood scientifically. Hence UNFCCC is a climate research promoter of highest calibre.
The translation of the above conditions into the challenges ahead can be made clear by the following questions:
1. At what temperature increase rate can forests no longer adapt? In other words: Can boreal forests move within a century by several hundred kilometers northward? West European forests could move in about 10,000 years from southern France to Northern Norway. Under Scenario A2 the same move would be squeezed into about a century. Certainly A2 would lead to the collapse of forest ecosystems, at least to such an extent that their services to us would be drastically diminished.
2. How strong must the precipitation belt shift be to generally endanger food supply for mankind? What can be tolerated? More food in mid and high latitudes while a serious food crisis leads to migration out of enlarged semi-arid zones, already suffering from desertification now?
3. At which total costs (adaptation plus mitigation) caused by climate change will sustainable economic development no longer be possible? How would countries, where these costs reach much higher percentages of the gross domestic product than in highly developed countries, get the proper support from these?
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