Members of the Intergovernmental Panel on Climate Change (IPCC) on Monday (March, 31) released the second instalment of the Fifth Assessment Report, concerning the impacts of climate change on human and natural systems, climate-related risks and vulnerabilities, options and benefits for adaptation.
The final draft and the Summary for Policymakers, approved line-by-line by scientists and government experts during a five-day meeting in Yokohama, Japan, are available online. It is part two of a four-part assessment, whose first part dealing with the physical science basis of climate change was published in September 2013. The Working Group III contribution, assessing mitigation policies and technologies, will be finalized in Berlin, Germany, on 7-11 April 2014, and a Synthesis Report will be completed in October.
Key message is that in recent decades climate change has caused “impacts on natural and human systems on all continents and across the oceans”, with strongest and most comprehensive evidence for natural systems and a major or minor contribution of climate change attributable to impacts on human systems, the report says. Observed impacts on natural systems vary across regions and encompass changing in precipitation, snow and ice melting, glaciers shrinking almost worldwide, terrestrial, freshwater, and marine species shifting their geographic ranges, seasonal activities, migration patterns, abundances, and species interactions. Climate change has negatively affected food production, especially wheat and maize yields. Rice and soybean has been less affected but IPCC agreed that “negative impacts of climate change on crop yields have been more common than positive impacts”. Consequences on human health has been relatively small compared with others stressors and not well quantified: the report pointed out global warming resulted in an increase in heat-related mortality and a decrease in cold-related mortality in some regions, and that local changes in temperature and rainfall have altered the distribution of some water-borne illnesses and disease vectors.
Ecosystems and many human systems proved to be significantly vulnerable to climate-related extremes events, such as heat waves, droughts, floods, cyclones, and wildfires. The IPCC assessed that vulnerability and exposure to climate impacts in human systems vary according to “non-climatic factors and from multidimensional inequalities” (socioeconomic status and income, gender, ethnicity, age, disabilities, or living in an area where violent conflicts occur) that determine the adaptive capacity to respond. Thus climate-related hazards are more dangerous for people already coping with poverty and harsh conditions, directly affecting them through impacts on livelihoods, reductions in crop yields, or destruction of homes and indirectly through increased food prices and food insecurity, the report says.
The Working Group II highlighted several key risks for the future, or rather “potentially severe impacts relevant to dangerous anthropogenic interference with the climate system”, involving “potentially large or irreversible consequences, high probability of consequences, and/or limited adaptive capacity”. These include risk of death and disrupted livelihoods due to sea level rise, coastal flooding and storm surges in low-lying coastal zones and small island developing states; food insecurity, particularly for poorer population, due to warming, droughts and precipitation variability (according to the report, “all aspects of food security are potentially affected by climate change, including food access, utilization, and price stability”); risk of severe harm due to inland flooding for large urban population; loss of livelihoods and income in rural areas due to insufficient access to drinking and irrigation water and reduced agricultural productivity; systemic risk of infrastructure networks breakdown due to extreme weather events; loss of terrestrial and marine ecosystems, and the services they provide, especially for fishing communities in tropical areas and the Arctic; increased mortality and incidence of diseases due to extreme heat, particularly for more vulnerable urban population. Specific risks involve urban and rural areas, energy sectors and global economic impacts. The IPCC estimated that an additional warming of around 2°C will lead to an annual economic loss of 0.2-2.0% of global income. Estimates do not account for catastrophic changes, tipping points, and other factors, and scientists specified that “losses are more likely than not to be greater, rather than smaller, than this range”.
According to IPCC, risks will vary through time across regions and populations, and the report provides an assessment of key risks and potential for adaptation for each region. For Europe, for instance, the highest risks are from changes in water availability (water shortages and heavy precipitation) and heat. Wildfires, heat waves and flooding are the biggest risks for North America. South America and Asia are also exposed to drought-related food shortages, and population in Africa will face extra risks of pests and disease. Australia and New Zealand risk losing the unique coral reef ecosystems, and small island nations are already facing coastal erosion and loss of land due to sea level rise.
Scientists summarized risks into five Reasons for Concern (updated from previous assessment reports), regarding unique and threatened systems, extreme weather events, unevenly distribution of impacts, global aggregate impacts and large scale singular events, ranging from the firsts being already at risk or exacerbated by current warming and projected to increase with additional warming of around 1°C, and the risk of abrupt and irreversible changes, such as the complete loss of the Greenland ice sheet, increasing disproportionately with a 1-2°C of additional warming and becoming high above 3°C.
The IPCC agreed that while a certain amount of impacts are unavoidable, “the overall risks of climate change impacts can be reduced by limiting the rate and magnitude of climate change”, thus by reducing GHG emissions. Adaptation can reduce exposure and vulnerability for human systems, and provides also co-benefits. Measures to cope with climate-related risks are “place and context specific”, and it must be planned and implemented through complementary actions involving individuals to governments, the report says.