Future forecast: ‘extreme effects’ of global warming

Longer summers, more frequent tornadoes, rising sea levels, more extreme storms and heatwaves, desiccating soils and drought are among the effects expected to be brought on by rising global temperatures by the end of the century, according to a new report.

Global temperatures are set to hit the “severely stressed” thresholds we would need to see in order to undermine the performance of some species of ecosystems and make some species vulnerable to extinction, according to findings of the Carnegie Institution’s “HeatMap for the Globe”. The report is the largest analysis of the impacts of rising global temperatures on the flora and fauna of the planet so far published. It is based on a detailed analysis of the 17 most useful and important ecosystems for human life, including a range of wildlife, crop, crop ecosystem, mountain man and maritime ecosystems, coral reefs, freshwater ecosystems, and climate zones.

Experts say that climate change will drive more severe heatwaves, causing more and longer droughts and wildfires. For example, the longest summer heatwave ever recorded in the US, in California in 2003, was 93 days, whereas current summers are now 23 days longer than they were in 1750. Longer, hotter summers will be more destructive to crop output and possibly production of crops, but the impact could be mitigated by practices such as irrigation and the use of less polluting fuels. Longer, hotter summers could also be enhanced by a warmer trend in humidity.

The Carnegie study also warns of damage to tropical bird flocks and animal communities along the US Atlantic coast, and extreme risk to species and ecosystems from sea level rise, both of which are already showing up in some areas in temperature-driven surges. A study of the effects of rising sea levels on coral reefs from rising ocean temperatures in the Gulf of Mexico found reefs are responding to warmer water by shedding more calcium and making reefs more brittle and unviable.

Climate change, it says, could also be a threat to the broader global food supply if warm, wetter winters lead to longer, hotter growing seasons in parts of South America, while droughts in western India could cause crop failure, and more fires in Australia’s vast rainforests. In Caribbean regions, where most plants and animals are dependent on warmer conditions, climate change could cut off communities from farmland, cutting off them from food supplies.

Global warming could also have direct impacts on our ways of life, from heat waves and bushfires to potential death from rising seas. Corals, for example, rely on water in the warmer winters when they are hardiest, so climate change could mean they come under further stress in the winter if temperatures in the area drop to freezing or below. The study suggests that water availability in the regions where farmers grow most of their produce will also be affected.

Each of the 17 ecosystems studied had changes in ecology and productivity of varying intensity since 1980, ranging from low to severe stress. The most abundant group of landscapes was the oceans, led by the Antarctic, followed by terrestrial ecosystems, primarily tropical rainforests. Each habitat had climate change impacts or impacts stemming from an increase in climate risk.

Kevin Arrigo, the report’s lead author, said: “Most ecosystems are resilient. However, we are beginning to see some of the sectors where the most extreme impacts are likely to occur.”

The study claims that these intense stresses – impacts ranging from gradual depletion of land resources to war – would occur far more rapidly than if we fail to address climate change.

On average, each species could potentially lose about two-thirds of its key resources from increasing temperatures by 2050, while coral reefs – where 50% of the human species depend on food produced from their reefs – could expect significant losses by the end of the century.

“The variability of these impacts over time is pretty stark. We used a variety of computer model methods to investigate how quickly this [damage] might happen, over different time periods,” said Arrigo.

On the upside, all ecosystems would benefit from more intensive rainforests, which could produce two to three times more food without driving pests away from humans. But Arrigo added: “But every future depends on where this [widespread] benefit occurs. If you think trees are good for your community then you are probably going to have to accept a new level of risk.”

Climate change impacts are already occurring. Nasa said on Thursday that it had found that 2012 was the hottest year in the US since records began in 1895.

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