Efficient measures to stop human-induced climate change involve, first and foremost, reducing direct carbon emissions. This is the only way of effectively combating the anthropogenic greenhouse effect – whereby rising greenhouse gas concentrations cause the atmosphere to warm up. However, the atmosphere has a long memory and it takes a long time for greenhouse gases to degrade. They can continue to exert their effects for decades. Model results show that even if all additional carbon emissions had been shut off in 2000, the global average temperature would still have risen by a further 0.4°C by 2100. The models indicate that if greenhouse gas emissions continue unchecked, we will face an increase of as much as 4.8°C by 2100 (compared to the reference period of 1986 to 2005). Stopping this trend is a global task – one that has been the subject of numerous rounds of international climate talks and should now become binding at the UN climate conference in Paris in autumn 2015. The aim of the summit is to produce an agreement that will enter into force from 2020. Unlike the Kyoto Protocol (agreed in 1997, entered into force in 2005), which set out targets for carbon emissions in industrialised countries, the new agreement should incorporate obligations for all industrialised, newly industrialised and developing countries. The aim is to reduce greenhouse gas emissions in all 194 countries that have ratified the UN Framework Convention on Climate Change. An ambitious reduction in greenhouse gas emissions is the only way to limit average global warming to a maximum of 2°C between now and 2100. That is the temperature increase experts believe we will be able to manage.
This question was answered by Dr Klaus Grosfeld, Managing Director of the Helmholtz Climate Initiative REKLIM (Regional climate change).