During a side event held by the Federal States of Micronesia Hermann Held gave a short lecture on tipping elements in the Earth’s climate system, where global warming through positive feedback mechanisms leads to self-propelling change. Held has co-authored a compilation of the nine most policy-relevant potential tipping elements, such as the Greenland ice sheet or the Amazon rainforest. He also contributed to the identification of characteristic symptoms that may also indicate future abrupt changes induced by global warming.
Sea level rise is regarded as one of the severest climate impacts. Since the IPCC’s Fourth Assessment Report was published in early 2007 a number of scientific publications have shed light on sea level rise due to global warming. The IPCC’s projection of up to 59 centimetres (about 23 inches) by 2100 did not include the contribution of rapid changes in ice flow, which cannot be computed for the future, but are already observed to occur today. Recent satellite data show that ice loss from Greenland and Antarctica has contributed about 40 percent to the sea level rise of the past five years, Stefan Rahmstorf reported in a side event organised by the North-South Initiative Germanwatch. Rahmstorf’s own semi-empirical approach suggested a possible global sea level rise of 0.5 to 1.4 metres (about 20 to 55 inches) above the 1990 level by 2100. Keeping global warming below two degrees Celsius could keep sea level rise well below this, though.
However, reaching this goal the European Union has set itself would require a broad portfolio of mitigation options and probably negative emissions, Brigitte Knopf reported in a side event held jointly by the Worldwide Fund for Nature (WWF) and the EU’s ADAM project, in which PIK is a partner. Negative emissions could be generated through the use of biomass as a fuel for power generation in combination with carbon capture and sequestration. Keeping the two degrees goal with a high likelihood appears to be technically feasible and economically viable at moderate costs, Knopf concluded.
The costs of a global climate stabilization agreement have been jointly investigated by researchers from the Euro-Mediterranean Centre on Climate Change (CMCC), the International Research Centre on the Environment and Development (CIRED) and PIK. In their side event called “The true costs of climate policy” Ottmar Edenhofer reported that costs crucially depend on the timing of when the different countries participate in a global carbon market. An important finding is a “first-mover advantage” for the EU if it takes unilateral action in reducing emissions. The researchers presented their assessment and recommendations from a suite of state-of-the-art European models.
