Potsdam, Germany

The Potsdam Institute for Climate Impact Research , is a government-funded research institute addressing crucial scientific questions in the fields of global change, climate impacts and sustainable development. Ranked among the top environmental think tanks worldwide, it is one of the leading research institutions and part of a global network of scientific and academic institutions working on questions of global environmental change. It is a member of the Leibniz Association, whose institutions perform research on subjects of high relevance to society. Wikipedia.

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Schwanitz V.J.,Potsdam Institute for Climate Impact Research
Environmental Modelling and Software | Year: 2013

Integrated Assessment Models of global climate change (IAMs) are an established tool to study interlinkages between the human and the natural system. Insights from these complex models are widely used to advise policy-makers and to inform the general public. But up to now there has been little understanding of how these models can be evaluated and community-wide standards are missing. To answer this urgent question is a challenge because the systems are open and their future behavior is fundamentally unknown. In this paper, we discuss ways to overcome these problems. Reflecting on experience from other modeling communities, we develop an evaluation framework for IAM of global climate change. It builds on a systematic and transparent step-by-step demonstration of a model's usefulness testing the plausibility of its behavior. Steps in the evaluation hierarchy are: setting up an evaluation framework, evaluation of the conceptual model, code verification and documentation, model evaluation, uncertainty and sensitivity analysis, documentation of the evaluation process, and communication with stakeholders. An important element in evaluating IAM of global climate change is the use of stylized behavior patterns derived from historical observation. The discussion of two examples is offered in this paper. © 2013 Elsevier Ltd.

Gerten D.,Potsdam Institute for Climate Impact Research
Hydrology and Earth System Sciences | Year: 2013

This paper argues that the interplay of water, carbon and vegetation dynamics fundamentally links some global trends in the current and conceivable future Anthropocene, such as cropland expansion, freshwater use, and climate change and its impacts. Based on a review of recent literature including geographically explicit simulation studies with the process-based LPJmL global biosphere model, it demonstrates that the connectivity of water and vegetation dynamics is vital for water security, food security and (terrestrial) ecosystem dynamics alike. The water limitation of net primary production of both natural and agricultural plants - already pronounced in many regions - is shown to increase in many places under projected climate change, though this development is partially offset by water-saving direct CO2 effects. Natural vegetation can to some degree adapt dynamically to higher water limitation, but agricultural crops usually require some form of active management to overcome it - among them irrigation, soil conservation and eventually shifts of cropland to areas that are less water-limited due to more favourable climatic conditions. While crucial to secure food production for a growing world population, such human interventions in water-vegetation systems have, as also shown, repercussions on the water cycle. Indeed, land use changes are shown to be the second-most important influence on the terrestrial water balance in recent times. Furthermore, climate change (warming and precipitation changes) will in many regions increase irrigation demand and decrease water availability, impeding rainfed and irrigated food production (if not CO2 effects counterbalance this impact - which is unlikely at least in poorly managed systems). Drawing from these exemplary investigations, some research perspectives on how to further improve our knowledge of human-water-vegetation interactions in the Anthropocene are outlined. © Author(s) 2013. CC Attribution 3.0 License.

Muller C.,Potsdam Institute for Climate Impact Research
Annual Review of Nutrition | Year: 2013

Climate change impact assessments on agriculture are subject to large uncertainties, as demonstrated in the present review of recent studies for Africa. There are multiple reasons for differences in projections, including uncertainties in greenhouse gas emissions and patterns of climate change; assumptions on future management, aggregation, and spatial extent; and methodological differences. Still, all projections agree that climate change poses a significant risk to African agriculture. Most projections also see the possibility of increasing agricultural production under climate change, especially if suitable adaptation measures are assumed. Climate change is not the only projected pressure on African agriculture, which struggles to meet demand today and may need to feed an additional one billion individuals by 2050. Development strategies are urgently needed, but they will need to consider future climate change and its inherent uncertainties. Science needs to show how existing synergies between climate change adaptation and development can be exploited. © 2013 by Annual Reviews. All rights reserved.

Hirth L.,Potsdam Institute for Climate Impact Research
Energy Journal | Year: 2015

This paper estimates the welfare-optimal market share of wind and solar power, explicitly taking into account their output variability. We present a theoretical valuation framework that consistently accounts for the impact of fluctuations over time, forecast errors, and the location of generators in the power grid on the marginal value of electricity from renewables. Then the optimal share of wind and solar power in Northwestern Europe's generation mix is estimated from a calibrated numerical model.We find the optimal long-term wind share to be 20%, three times more than today; however, we also find significant parameter uncertainty. Variability significantly impacts results: if winds were constant, the optimal share would be 60%. In addition, the effect of technological change, price shocks, and policies on the optimal share is assessed. We present and explain several surprising findings, including a negative impact of CO2 prices on optimal wind deployment. Copyright © 2015 by the IAEE. All rights reserved.

Feulner G.,Potsdam Institute for Climate Impact Research
Atmospheric Chemistry and Physics | Year: 2011

Apparent evidence for a strong signature of solar activity in ground-based insolation data was recently reported. In particular, a strong increase of the irradiance of the direct solar beam with sunspot number as well as a decline of the brightness of the solar aureole and the measured precipitable water content of the atmosphere with solar activity were presented. The latter effect was interpreted as evidence for cosmic-ray-induced aerosol formation. Here I show that these spurious results are due to a failure to correct for seasonal variations and the effects of volcanic eruptions and local pollution in the data. After correcting for these biases, neither the atmospheric water content nor the brightness of the solar aureole show any significant change with solar activity, and the variations of the solar-beam irradiance with sunspot number are in agreement with previous estimates. Hence there is no evidence for the influence of solar activity on the climate being stronger than currently thought. © 2011 Author(s).

Feulner G.,Potsdam Institute for Climate Impact Research
Reviews of Geophysics | Year: 2012

For more than four decades, scientists have been trying to find an answer to one of the most fundamental questions in paleoclimatology, the "faint young Sun problem." For the early Earth, models of stellar evolution predict a solar energy input to the climate system that is about 25% lower than today. This would result in a completely frozen world over the first 2 billion years in the history of our planet if all other parameters controlling Earth's climate had been the same. Yet there is ample evidence for the presence of liquid surface water and even life in the Archean (3.8 to 2.5 billion years before present), so some effect (or effects) must have been compensating for the faint young Sun. A wide range of possible solutions have been suggested and explored during the last four decades, with most studies focusing on higher concentrations of atmospheric greenhouse gases like carbon dioxide, methane, or ammonia. All of these solutions present considerable difficulties, however, so the faint young Sun problem cannot be regarded as solved. Here I review research on the subject, including the latest suggestions for solutions of the faint young Sun problem and recent geochemical constraints on the composition of Earth's early atmosphere. Furthermore, I will outline the most promising directions for future research. In particular I would argue that both improved geochemical constraints on the state of the Archean climate system and numerical experiments with state-of-the-art climate models are required to finally assess what kept the oceans on the Archean Earth from freezing over completely. Copyright 2012 by the American Geophysical Union.

Feulner G.,Potsdam Institute for Climate Impact Research
Geophysical Research Letters | Year: 2011

Estimates for the total solar irradiance (TSI) during the 17th-century Maunder Minimum published in the last few years have pointed towards a TSI difference of 0.2-0.7 W m-2 as compared to the 2008/2009 solar minimum. Two recent studies, however, give anomalies which differ from this emerging consensus. The first study indicates an even smaller TSI difference, placing the Maunder Minimum TSI on the same level as the 2008/2009 minimum. The second study on the other hand suggests a very large TSI difference of 5.8 W m-2. Here I use coupled climate simulations to assess the implications of these two estimates on Northern-hemisphere surface air temperatures over the past millennium. Using a solar forcing corresponding to the estimate of the first study, simulated Northern-hemisphere temperatures over the past millennium are consistent with reconstructed surface air temperatures. The large TSI differences between times of high and low solar activity as suggested by the second study, however, yield temperatures during all past grand solar minima that are too low, an excessive variance in Northern-hemisphere temperature on timescales of 50-100 years as compared to reconstructions, and temperatures during the first half of the 20th century which are too low and inconsistent with the instrumental temperature record. In summary this suggests a more moderate TSI difference of less than 1 W m-2 and possibly as low as 0-0.3 W m-2. Copyright 2011 by the American Geophysical Union.

Hinkel J.,Potsdam Institute for Climate Impact Research
Global Environmental Change | Year: 2011

The issue of " measuring" climate change vulnerability and adaptive capacity by means of indicators divides policy and academic communities. While policy increasingly demands such indicators an increasing body of literature criticises them. This misfit results from a twofold confusion. First, there is confusion about what vulnerability indicators are and which arguments are available for building them. Second, there is confusion about the kinds of policy problems to be solved by means of indicators. This paper addresses both sources of confusion. It first develops a rigorous conceptual framework for vulnerability indicators and applies it to review the scientific arguments available for building climate change vulnerability indicators. Then, it opposes this availability with the following six diverse types of problems that vulnerability indicators are meant to address according to the literature: (i) identification of mitigation targets; (ii) identification of vulnerable people, communities, regions, etc.; (iii) raising awareness; (iv) allocation of adaptation funds; (v) monitoring of adaptation policy; and (vi) conducting scientific research. It is found that vulnerability indicators are only appropriate for addressing the second type of problem but only at local scales, when systems can be narrowly defined and inductive arguments can be built. For the other five types of problems, either vulnerability is not the adequate concept or vulnerability indicators are not the adequate methodology. I conclude that both the policy and academic communities should collaboratively attempt to use a more specific terminology for speaking about the problems addressed and the methodologies applied. The one-size-fits-all vulnerability label is not sufficient. Speaking of " measuring" vulnerability is particularly misleading, as this is impossible and raises false expectations. © 2010 Elsevier Ltd.

Fussel H.-M.,Potsdam Institute for Climate Impact Research
Global Environmental Change | Year: 2010

While it is generally asserted that those countries who have contributed least to anthropogenic climate change are most vulnerable to its adverse impacts some recently developed indices of vulnerability to climate change come to a different conclusion. Confirmation or rejection of this assertion is complicated by the lack of an agreed metric for measuring countries' vulnerability to climate change and by conflicting interpretations of vulnerability. This paper presents a comprehensive semi-quantitative analysis of the disparity between countries' responsibility for climate change, their capability to act and assist, and their vulnerability to climate change for four climate-sensitive sectors based on a broad range of disaggregated vulnerability indicators. This analysis finds a double inequity between responsibility and capability on the one hand and the vulnerability of food security, human health, and coastal populations on the other. This double inequity is robust across alternative indicator choices and interpretations of vulnerability. The main cause for the higher vulnerability of poor nations who have generally contributed little to climate change is their lower adaptive capacity. In addition, the biophysical sensitivity and socio-economic exposure of poor nations to climate impacts on food security and human health generally exceeds that of wealthier nations. No definite statement can be made on the inequity associated with climate impacts on water supply due to large uncertainties about future changes in regional water availability and to conflicting indicators of current water scarcity. The robust double inequity between responsibility and vulnerability for most climate-sensitive sectors strengthens the moral case for financial and technical assistance from those countries most responsible for climate change to those countries most vulnerable to its adverse impacts. However, the complex and geographically heterogeneous patterns of vulnerability factors for different climate-sensitive sectors suggest that the allocation of international adaptation funds to developing countries should be guided by sector-specific or hazard-specific criteria despite repeated requests from participants in international climate negotiations to develop a generic index of countries' vulnerability to climate change. © 2010 Elsevier Ltd.

Coumou D.,Potsdam Institute for Climate Impact Research | Rahmstorf S.,Potsdam Institute for Climate Impact Research
Nature Climate Change | Year: 2012

The ostensibly large number of recent extreme weather events has triggered intensive discussions, both in- and outside the scientific community, on whether they are related to global warming. Here, we review the evidence and argue that for some types of extreme - notably heatwaves, but also precipitation extremes - there is now strong evidence linking specific events or an increase in their numbers to the human influence on climate. For other types of extreme, such as storms, the available evidence is less conclusive, but based on observed trends and basic physical concepts it is nevertheless plausible to expect an increase. © 2012 Macmillan Publishers Limited. All rights reserved.

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