14th October 2011
The latest science summarized below suggests that the impacts of climate change in many areas of the world are not advancing linearly: profound changes are already occurring and models project even greater changes for the remainder of the 21st Century. The findings support the need for rapid and deep cuts in greenhouse gas emissions, and at the same time confirm that climate adaptation measures are increasingly required today—and will be ever more important in the future—to enhance the resilience of both human communities and ecosystems. There is new and abundant literature on four topics: climate feedbacks where the literature generally suggests positive feedbacks from many different processes; sea level rise where the evidence indicates that previous estimates of sea level rise are likely to be revised upward; ocean acidification where new science is confirming the potential global implications of an ocean that is already 30 percent more acidic than about 100 years ago; and on climate impacts to ecological systems, where the literature base on climate impacts is broadened to provide more evidence of changes to a variety of species and discussion of our entering the sixth mass extinction of species that the planet has experienced. This review is divided into three sections:
- Physical Climate
- Hydrological Cycle
- Ecosystems and Ecosystem Services
2000–2009 was the warmest decade on record since 1880 (NASA, p. 4).
Models indicate that cumulative total anthropogenic carbon dioxide emissions need to be limited to 1 trillion tons in the future if global average temperature increase is to remain below 2° C (roughly one half of the 1 trillion tons have already been emitted) (Allen et al., p. 4).
The climate system has a number of different feedback mechanisms built into it, some of which are better known than others. New evidence suggests that as temperature rises, there may be positive feedbacks (processes that reinforce processes) through less cloud cover and in changes in aerosols, soils, peatlands, and Arctic ice cover (pages 6–11), which can lead to accelerated climate change impacts.
Recent estimated projections of future global sea level rise (Horton et al., Vermeer and Rahmstorf, Grinsted et al., and Jevrejeva et al., p. 11) have generally been significantly higher than estimates from the 2007 IPCC Report. Additionally, new estimates also suggest that global sea level could rise approximately 3.26 meters from the melting of the West Antarctic Ice Sheet. If perturbations in Earth’s rotation and shoreline migration are taken into account, the Pacific and Atlantic coasts of the United States, could be impacted by sea levels 25 percent higher than the global mean at the end of the century (Mitrovica et al., p. 12).
Observations show that multi-year (MY) winter sea ice area decreased by 42 percent between 2005 and 2008 and that there was a thinning of ~0.6 m in MY ice thickness over the same 4 years (average thickness of the seasonal ice in midwinter is ~2 m) (Kwok et al., p. 19).
As much as 12 percent of the volume of Swiss alpine glaciers was lost over the period from 1999 to 2008 (Farinotti et al., p. 17).
As glaciers melt, persistent organic pollutants are finding their way into “pristine” alpine lakes, representing a toxic “blast from the past” (Bogdal et al., p. 18).
The rate of mass loss in the East Antarctic Ice Sheet may be greater than previously estimated (Chen et al., p. 15).
Changing ice dynamics in the Arctic may be leading to an increase in observed “winter weather” including more snow and colder temperatures in temperate regions of the Northern Hemisphere (Francis et al. and Petoukhov et al., p. 21).
Ecosystems and Ecosystem Services:
New research suggests that while wildfire frequency increases in response to climate change globally, regional changes demonstrate both increases and decreases in wildfire distribution, largely mediated by regionally-specific vegetation, precipitation changes and CO2 fertilization (Krawchuk et al., p. 30).
Ocean acidification, which only recently was recognized a threat to coral in areas such as the Great Barrier Reef (and is happening much more quickly than anticipated (De’ath et al., p. 32), is now recognized as having implications for the entire ocean food web which is critical to whales, fish, and mollusks (snails and scallops) (Munday et al., Gooding et al. and Comeau et al., pages 33–34).
Based on human physiological estimates, a global average temperature increase of 7° C, which is toward the extreme upper part of the range of current projections, would make large portions of the world uninhabitable (Sherwood et al., p. 28).
The impacts of projected climate change on emperor penguin populations are likely to be significant; with a 36 percent probability of “quasi extinction” (greater than 95 percent decline) by 2100 (Jenouvrier et al., p. 25).
A 28 cm future sea level rise is projected to reduce the current Bengal tiger habitat in the Sundarban region of Bangladesh by 96 percent and would likely reduce tiger numbers to 20 breeding pairs (Loucks et al., p. 26). Climate Change Mitigation Technologies and Geoengineering:
Land-use change associated with planting biofuel crops can have implications on the regional average temperatures through an albedo effect (Georgescu et al., p. 39).
Advances in more flexible, cheaper small-scale solar photovoltaics could make it easier and less expensive to integrate solar-powered electricity generation into building materials (Lee et al., p. 36).
If all urban surfaces worldwide were made reflective, the heat trapping effects of urban surfaces would be eliminated, an impact greater than eliminating the annual anthropogenic emissions of the entire globe (Akbari et al., p. 41).
Geoengineering—“the deliberate large-scale manipulation of the planet’s environment to counteract climate change” (Royal Society 2009)—is being more widely studied in terms of its potential to limit global warming if efforts to reduce emissions fail, as well as its implications. Various proposals (and preliminary findings), grouped into two categories—carbon dioxide removal (CDR) and solar radiation management (SRM—are summarized here (pages 40–44).Credit : World Resource Institute