The anthropogenic climate change will persist if the global volume of greenhousegas emissions will not be reduced significantly. A dangerous and irreversibleclimate change will occur if atmospheric concentrations of greenhousegases in the year 2100 exceed 450 ppm and global surface temperatureis 2 C higher than its preindustrial level. The consequence of exceedingthese limits would be both more frequent and more violent extreme climateevents. In order to avoid this, it is necessary to stabilize global greenhousegas concentrations at nearly today's level.Significant emission reduction would require the countries that are primarilyresponsible immediately implementing emissions-reducing measures.If climate policy measures are not introduced, global climate changedamages amounting to up to 20 trillion US dollars can be expected in theyear 2100.1 If such measures are not implemented now, but only in 20 or30 years' time, it will not be possible to prevent the rise in global surfacetemperature exceeding the 2 C limit. Moreover, the costs of a climate protectionpolicy launched today are likely to be lower than a policy initiatedonly in 20 years' time, which would then be based on drastic measures. Thesooner a policy of climate protection is implemented, the fewer climatechange damages humankind will face in future decades. The costs of anactive climate protection policy implemented today would reach globallyaround 430 billion US dollars in 2050 and around 3 trillion US dollars in2100. A climate protection policy that entered into force only in 2025 wouldimply additional costs of up to 50 billion US dollars in 2050 and 340 billionUS dollars in 2100. Global climate damages of up to 12 trillion US dollarscan be avoided in 2100 if active climate protection policy is implemented asrapidly as possible.In Germany, a climate protection policy that immediately implementseffective measures would cost 5.7 billion US dollars in 2050 and 40 billionUS dollars in 2100. At the same time, however, climate change damagesamounting to 33 billion US dollars in 2050 and 160 billion US dollars in 2100would be avoided.