A changing climate creates pervasive risks

Climate change is projected to increase inter-annual variability of crop yields in many regions. Here a Somali woman waiting for medical assistance during a drought in 2011. Photo: United Nations Photo/flickr.com/cc by-nc-nd

The effects of climate change are already being seen on all continents and across the oceans.

The Intergovernmental Panel on Climate Change (IPCC) issued a report in March 2014 that details the impacts of climate change to date, the future risks from a changing climate, and the opportunities for effective action to reduce risks. The report, called “Climate Change 2014: Impacts, Adaptation, and Vulnerability”, concludes that responding to climate change involves making choices about risks in a changing world and that the nature of the risks of climate change is increasingly clear. The report identifies vulnerable people, industries, and ecosystems around the world.

Increasing magnitudes of warming increase the likelihood of severe and pervasive impacts that may be surprising or irreversible according to the IPCC. “Observed impacts of climate change have already affected agriculture, human health, ecosystems on land and in the oceans, water supplies, and some people’s livelihoods. The striking feature of observed impacts is that they are occurring from the tropics to the poles, from small islands to large continents, and from the wealthiest countries to the poorest.”
Rajendra Pachauri, Chair of the IPCC, said: “The Working Group II report is another important step forward in our understanding of how to reduce and manage the risks of climate change. Along with the reports from Working Group I and Working Group III, it provides a conceptual map of not only the essential features of the climate challenge but the options for solutions.”

The report communicates the degree of certainty in each key finding of the assessment based on evidence (limited, medium, or robust); agreement (low, medium, or high); confidence (very low, low, medium, high, and very high).

The IPCC says that evidence of climate-change impacts is strongest and most comprehensive for natural systems. Many terrestrial, freshwater, and marine species have shifted their geographic ranges, seasonal activities, migration patterns, abundances, and species interactions in response to ongoing climate change (high confidence). While only a few recent species extinctions have been attributed as yet to climate change (high confidence), natural global climate change at rates slower than current anthropogenic climate change caused significant ecosystem shifts and species extinctions during the past millions of years (high confidence).

For the major crops (wheat, rice, and maize) in tropical and temperate regions, climate change without adaptation is projected to negatively impact production for local temperature increases of 2°C or more above late-20th-century levels, although individual locations may benefit (medium confidence). Projected impacts vary across crops and regions and adaptation scenarios, with about 10% of projections for the period 2030–2049 showing yield gains of more than 10%, and about 10% of projections showing yield losses of more than 25%, compared to the late 20th century. After 2050 the risk of more severe yield impacts increases and depends on the level of warming. Climate change is projected to progressively increase inter-annual variability of crop yields in many regions. These projected impacts will occur in the context of rapidly rising crop demand.
 

All aspects of food security are potentially affected by climate change, including food access, utilization, and price stability (high confidence). Redistribution of marine fisheries catch potential towards higher latitudes poses risk of reduced supplies, income, and employment in tropical countries, with potential implications for food security (medium confidence). Global temperature increases of ~4°C or more above late-20th-century levels, combined with increasing food demand, would pose large risks to food security globally and regionally (high confidence). Risks to food security are generally greater in low-latitude areas.
 

The key risks for coastal zones, small islands and oceans, all of which are identified with high confidence, are the following according to the IPCC:

“- Risk of death, injury, ill-health, or disrupted livelihoods in low-lying coastal zones and small island developing states and other small islands, due to storm surges, coastal flooding, and sea-level rise.
- Systemic risks due to extreme weather events leading to breakdown of infrastructure networks and critical services such as electricity, water supply, and health and emergency services.
- Risk of loss of marine and coastal ecosystems, biodiversity, and the ecosystem goods, functions, and services they provide for coastal livelihoods, especially for fishing communities in the tropics and the Arctic.
- Unique and threatened systems: Some unique and threatened systems, including ecosystems and cultures, are already at risk from climate change (high confidence). The number of such systems at risk of severe consequences is higher with additional warming of around 1°C. Many species and systems with limited adaptive capacity are subject to very high risks with additional warming of 2°C, particularly Arctic-sea-ice and coral-reef systems.
- Large-scale singular events: With increasing warming, some physical systems or ecosystems may be at risk of abrupt and irreversible changes. Risks associated with such tipping points become moderate between 0–1°C additional warming, due to early warning signs that both warm-water coral reef and Arctic ecosystems are already experiencing irreversible regime shifts (medium confidence). Risks increase disproportionately as temperature increases between 1–2°C additional warming and become high above 3°C, due to the potential for a large and irreversible sea-level rise from ice sheet loss. For sustained warming greater than some threshold, near-complete loss of the Greenland ice sheet would occur over a millennium or more, contributing up to 7m of global mean sea-level rise.
- Due to sea-level rise projected throughout the 21st century and beyond, coastal systems and low-lying areas will increasingly experience adverse impacts such as submergence, coastal flooding, and coastal erosion (very high confidence). The population and assets projected to be exposed to coastal risks as well as human pressures on coastal ecosystems will increase significantly in the coming decades due to population growth, economic development, and urbanization (high confidence).
- Due to projected climate change by the mid-21st century and beyond, global marine-species redistribution and marine-biodiversity reduction in sensitive regions will challenge the sustained provision of fisheries productivity and other ecosystem services (high confidence). Spatial shifts of marine species due to projected warming will cause high-latitude invasions and high local-extinction rates in the tropics and semi-enclosed seas (medium confidence).
- For medium- to high-emission scenarios, ocean acidification poses substantial risks to marine ecosystems, especially polar ecosystems and coral reefs, associated with impacts on the physiology, behaviour, and population dynamics of individual species from phytoplankton to animals (medium to high confidence). Highly calcified molluscs, echinoderms, and reef-building corals are more sensitive than crustaceans (high confidence) and fish (low confidence), with potentially detrimental consequences for fisheries and livelihoods. Ocean acidification acts together with other global changes (e.g. warming, decreasing oxygen levels) and with local changes (e.g. pollution, eutrophication) (high confidence). Simultaneous drivers, such as warming and ocean acidification, can lead to interactive, complex, and amplified impacts for species and ecosystems.”
 

Further impacts of climate change on humans and the natural environment identified by the IPCC in the report will be presented in the next issue of Acid News

Reinhold Pape

The Working Group II contribution to the IPCC Fifth Assessment Report (WGII AR5) is available at www.ipcc-wg2.gov/AR5 and www.ipcc.ch.

Impacts of climate change and where they are expected to hit.