»Wetterextreme scheinen unvermeidlich geworden zu sein«

Executive Summary

The data show that dramatic climate changes, heat and weather extremes are already impacting people, damaging crops and coastlines and putting food, water, and energy security at risk. Across the three regions studied in this report, record-breaking temperatures are occurring more frequently, rainfall has increased in intensity in some places, while drought-prone regions are getting dryer. In an overview of social vulnerability, the poor and underprivileged, as well as the elderly and children, are found to be often hit the hardest. There is growing evidence, that even with very ambitious mitigation action, warming close to 1.5°C above pre-industrial levels by mid-century is already locked-in to the Earth’s atmospheric system and climate change impacts such as extreme heat events may now be unavoidable. If the planet continues warming to 4°C, climatic conditions, heat and other weather extremes considered highly unusual or unprecedented today would become the new climate normal – a world of increased risks and instability. The consequences for development would be severe as crop yields decline, water resources change, diseases move into new ranges, and sea levels rise. The task of promoting human development, of ending poverty, increasing global prosperity, and reducing global inequality will be very challenging in a 2°C world, but in a 4°C world there is serious doubt whether this can be achieved at all. Immediate steps are needed to help countries adapt to the climate impacts being felt today and the unavoidable consequences of a rapidly warming world. The benefits of strong, early action on climate change, action that follows clean, low carbon pathways and avoids locking in unsustainable growth strategies, far outweigh the costs. Many of the worst projected climate impacts could still be avoided by holding warming to below 2°C. But, the time to act is now.

This report focuses on the risks of climate change to development in Latin America and the Caribbean, the Middle East and North Africa, and parts of Europe and Central Asia. Building on earlier Turn Down the Heat reports this new scientific analysis examines the likely impacts of present day (0.8°C), 2°C and 4°C warming above pre-industrial temperatures on agricultural production, water resources, ecosystem services and coastal vulnerability for affected populations.

Scope of the Report

This third report in the Turn Down the Heat series covers three World Bank regions: Latin America and the Caribbean (LAC); the Middle East and North Africa (MENA); and parts of Europe and Central Asia (ECA). The focus is on the risks of climate change to development. While covering a range of sectors, special attention is paid to projected impacts on food and energy systems, water resources, and ecosystem services. The report also considers the social vulnerability that could magnify or moderate the climate change repercussions for human well-being. The report complements the first Turn Down the Heat report (2012) that offered a global overview of climate change and its impacts in a 4°C world and concluded that impacts are expected to be felt disproportion- ately in developing countries around the equatorial regions. Also, it extends the analysis in the second report (2013) that focused on the consequences of climate change for present day, 2°C, and 4°C warming above pre-industrial levels in Sub-Saharan Africa, South Asia, and South East Asia and demonstrated the potential of early onset of impacts at lower levels of warming.

This analysis draws on the Intergovernmental Panel on Cli- mate Change (IPCC) Fifth Assessment Report (AR5) Working Group reports released in 2013 and 2014, as well as peer-reviewed literature published after the cutoff dates for AR5. The few cases where there are significant differences in interpretation of projected impacts from the IPCC assessments (such as for sea-level rise and El Niño) are highlighted and explained.

The Global Picture

This report reaffirms earlier assessments, including the IPCC AR5 and previous Turn Down the Heat reports, that in the absence of near-term mitigation actions and further commitments to reduce emissions the likelihood of 4°C warming being reached or exceeded this century has increased. Under current policies there is about a 40 percent chance of exceeding 4°C by 2100 and a 10 percent chance of exceeding 5°C. However, many of the worst projected climate impacts in this report could still be avoided by holding warming below 2°C.

Selected Key Findings from Across the Regions

At the current level of 0.8°C warming above pre-industrial levels, adverse impacts of climate change have already been observed. Examples include:

• Extreme heat events are occurring more frequently.Theoccur- rence of record-breaking monthly mean temperatures has been attributed to climate change with 80 percent probability.

• Extreme precipitation has increased in frequency and intensity in many places.

• A robust drying trend has been observed for already drought- prone regions such as the Mediterranean.

• A significant increase in tropical North Atlantic cyclone activity has been observed and is affecting the Caribbean and Central America.

Under future climate change scenarios projected impacts include:

1. Highly unusual and unprecedented heat extremes: State-of-the-art climate modeling shows that extreme heat events increase not only in frequency but also impact a larger area of land under unabated warming. The prevalence of highly unusual and unprecedented heat extremes increases rapidly under an emissions pathway associated with a 4°C world.

Highly unusual heat extremes are similar to those experienced in Russia and Central Asia in 2010 and the United States in 2012 and unprecedented heat extremes refer to events essentially absent under present day climate conditions. Unprecedented heat extremes would likely remain largely absent in a 2°C world but in a 4°C world, could affect 70–80 percent of the land area in the Middle East and North Africa and Latin America and the Caribbean and approximately 55 percent of the land area in the parts of Europe and Central Asia assessed in this report.

2. Rainfall regime changes and water availability: Precipitation changes are projected under continued warming with substantial, adverse consequences for water availability. Central America, the Caribbean, the Western Balkans, and the Middle East and North Africa stand out as hotspots where precipitation is projected to decline 20–50 percent in a 4°C world. Conversely, heavy precipitation events are projected to intensify in Central and Eastern Siberia and northwestern South America with precipitation intensity increasing by around 30 percent and flooding risks increasing substantially in a 4°C world.

• In the Western Balkans and Central Asia, water availability becomes a threat as temperatures rise toward 4°C. With earlier glacier melt in Central Asia shifting the timing of water flows, and a higher risk of drought in the Balkans, this carries consequences for crop yields, urban health, and energy generation. In Macedonia, for example, there could be yield losses of up to 50 percent for maize, wheat, vegetables and grapes at 2°C warming. Flood risk is expected to increase slightly along the Danube, Sava and Tisza rivers.

3. Agricultural yields and food security: Significant crop yield impacts are already being felt at 0.8°C warming, and as temperatures rise from 2°C to 4°C, climate change will add further pressure on agricultural systems.

• The risks of reduced crop yields and production losses increase rapidly above 1.5°–2°C warming. In the Middle East and North Africa and the Latin America and the Caribbean regions, without further adaptation actions, strong reductions in potential yield are projected for around 2°C warming. For example, a 30–70 percent decline in yield for soybeans and up to 50 percent decline for wheat in Brazil, a 50 percent decrease for wheat in Central America and the Caribbean, and 10–50 percent reduction for wheat in Tunisia. Projected changes in potential crop yields in Central Asia are uncertain at around 2°C warming. Increasing droughts and flood- ing events represent a major risk for agriculture in the Western Balkans.

• While adaptation interventions and CO2 fertilization may compensate for some of the adverse effects of climate change below 2°C warming, this report reaffirms the findings of the IPCC AR5 that under 3–4°C warming large negative impacts on agricultural productivity can be expected. There is some empirical evidence that, despite possible positive CO2 fertilization effects lead- ing to increased productivity, higher atmospheric levels of carbon dioxide could result in lowered protein and micronutrient (iron and zinc) levels of some major grain crops (e.g., wheat and rice).

• The projected impacts on subsistence and export crops production systems (e.g., soybeans, maize, wheat, and rice) would be felt at the local, national, and global levels. While global trade can improve food security and pro- tect against local shocks, there is a possibility for some regions to become over dependent on food imports and thus more vulnerable to weather events in other world regions and to the interruption of imports because of export bans in those regions.

4. Terrestrial Ecosystems: Ecosystem shifts are projected with increasing temperatures and changes in precipitation patterns significantly diminishing ecosystem services. This would have major repercussions on, for example, the global carbon cycle. For example:

• Projected increases in heat and drought stress, together with continuing deforestation, substantially increase the risk of large-scale forest degradation (reduction in forest biomass and area) in the Amazon rainforest. This could turn this carbon sink of global importance into a source of carbon; this has already been observed as a consequence of the severe droughts in 2005 and 2010 when scientists estimated that the Amazon faced a decrease in carbon storage of approximately 1.6 Pg carbon (2005) and 2.2 Pg carbon (2010) compared to non-drought years.

• Russia’s permafrost regions and boreal forests are sensitive to changes in temperature that could lead to productivity increases. But there is a risk of increasing disturbances, such as fires and pests, leading to widespread tree mortal- ity. Forest dieback and thawing of permafrost threaten to amplify global warming as stored carbon and methane are released into the atmosphere, giving rise to a self- amplifying feedback loop. With a 2°C warming, methane emissions from permafrost thawing could increase by 20–30 percent across boreal Russia.

5. Marine ecosystems: Substantial, adverse effects on marine ecosystems and their productivity are expected with rising temperatures, increases in ocean acidity, and likely reductions in available oxygen due to their combined effects. Observed rates of ocean acidification are already the highest in 300 million years and rates of sea level rise are the highest for 6,000 years.

Projections of coral bleaching indicate that preserving more than 10 percent of these unique ecosystems calls for limiting global warming to 1.5°C. Reef-building corals are critical for beach formation, coastal protection, fisheries, and tourism.

Physiological changes to fish and fish larvae have been observed and are expected with future ocean acidification. Below 2°C warming and without taking into account changes in ocean acidity, fishery catches in a number of locations are projected to markedly decrease by 2050 as fish populations migrate towards cooler waters.

6. Sea-level rise: In a 1.5°C world sea level rise is projected to increase by 0.36 m (range of 0.20 m to 0.60 m) and by 0.58 m (range of 0.40 m to 1.01 m) in a 4°C world for the period 2081–2100 compared to the reference period 1986–2005.8 Due to the time lag in the oceans’ response and the long response time of the Greenland and Antarctic ice sheets to atmospheric temperatures (thermal inertia) sea levels will continue to rise for many centuries beyond 2100.

• Sea-level rise poses a particular threat to urban communi- ties in the Middle East and North Africa and Latin America and the Caribbean, where large urban settlements and important infrastructure are situated along coastlines. The impact of rising sea levels will be particularly severe for the Caribbean island communities as possibilities for retreat are extremely limited. Rising sea levels will substantially increase the risk posed by storm surges and tropical cyclones, in particular for highly exposed small island states and low-lying coastal zones. In addition, rising sea levels could contribute to increased salt-water intrusion in freshwater aquifers (particularly in the Middle East and North Africa), a process made worse by other climate impacts (e.g., reduction in water availability) and other human-induced drivers (e.g., resource overuse).

7. Glaciers: A substantial loss of glacier volume and extent has been observed under current levels of warming in the Andes and Central Asia. Increasing glacial melt poses a high risk of flooding and severely reduces freshwater resources during crop growing seasons. It can also have negative impacts on hydropower supply.

• Tropical glaciers in the Central Andes have lost large amounts of ice volume throughout the 20th century and complete deglaciation is projected in a 4°C world. In Peru it is estimated that a 50 percent reduction in glacier runoff would result in a decrease in annual power output of approximately 10 percent, from 1540 gigawatt hours (GWh) to 1250 GWh.

• Since the 1960s Central Asian glaciers have reduced in area by 3–14 percent depending on their location. Further substantial losses of around 50 percent and up to 80 percent are projected for a 2°C and a 4°C world respectively. As a result, river flows are expected to shrink by 25 percent at around 3°C warming during the summer

months when water demand for agriculture is highest.

• In Central Asia hydropower generation has the potential to play a major role in the future energy mix however the predicted changes in runoff distribution will mean that there will be less water available for energy generation in summer months when it will compete with demands

from agriculture.

8. Social Vulnerability to Climate Change: The social impacts of climate change are hard to predict with certainty as they depend on climatic factors and their interaction with wider development trends. However, there is clear evidence that climate change is already affecting livelihoods and wellbe- ing in parts of the three regions and is likely to do so to a significantly greater extent if more extensive climate change occurs (Box 2). Where governance is weak, or infrastructure outdated or insufficient (as in parts of all three regions), this is likely to amplify the social challenges associated with adapting to further climate change.

Eine ausführliche Zusammenfassung des Berichts finden Sie hier (pdf).

Den vollständigen Bericht finden Sie hier (pdf).