Potential Abrupt Climate Change or Impact and Key Examples of Consequences Current Trend Near Term Outlook (for an Abrupt Change within This Century) Long Term Outlook (for a Significant Change1 after 2100) Level of Scientific Understanding Critical Needs (Research, Monitoring, etc.)
Abrupt Changes in Ecosystems Rapid state changes in ecosystems, species range shifts, and species boundary changes

• Extensive habitat loss

• Loss of ecosystem services

• Threats to food and water supplies

Species range shifts significant; others not clearly detected Moderate High Moderate

• Long term remote sensing and in-situ studies of key systems

• Improved hydrological and ecological models

Increases in extinctions of marine and terrestrial species

• Loss of high percentage of coral reef ecosystems (already underway)

• Significant percentage of land mammal, bird, and amphibian species extinct or endangered7

Species and population losses accelerating (Portion attributable to climate is uncertain) High Very high Moderate

• Better understanding of how species interactions and ecological cascades might magnify extinctions intensity

• Better understanding of how interactions between climate-caused extinctions and other extinction drivers (habitat fragmentation, overexploitation, etc.) multiply extinction intensity

• Improved monitoring of key species

1 Change could be either abrupt or non-abrupt.

2 To clarify, the Committee assesses the near-term outlook that sea level will rise abruptly before the end of this century as Low; this is not in contradiction to the assessment that sea level will continue to rise steadily with estimates of between 0.26 and 0.82 m by the end of this century (IPCC, 2013).

3 Methane is powerful but short-lived greenhouse gas.

4 Limited by ability to predict methane production from thawing organic carbon

5 No mechanism proposed would lead to abrupt release of substantial amounts of methane from ocean methane hydrates this century.

6 Limited by uncertainty in hydrate abundance in near-surface sediments, and fate of CH4 once released

7 Species distribution models (Thuiller et al., 2006) indicate between 10–40% of mammals now found in African protected areas will be extinct or critically endangered by 2080 as a result of modeled climate change. Analyses by Foden et al.(2013) and Ricke et al. (2013) suggest 41% of bird species, 66% of amphibian species, and between 61% and 100% of corals that are not now considered threatened with extinction will become threatened due to climate change sometime between now and 2100.

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