The latest UN Intergovernmental Panel on Climate Change (IPCC) report alarmingly warned today that it was vital for the world to phase out fossil fuels by 2100.
The committee claimed that cutting greenhouse gas emissions by between 40 per cent and 70 per cent by 2050, and to near or below zero emissions in 2100 "would likely keep warming <2°C."
Its chair Rajendra Pachauri warned during a press conference in Copenhagen, Denmark on Sunday morning, according to official tweets from the IPCC, that "climate change will leave no part of the world untouched."
He added that the "costs of inaction" were "much higher than the costs of action. Inaction would create increasing risks to economic growth."
IPCC chair of Working Group I Thomas Stocker said: “Our assessment finds that the atmosphere and oceans have warmed, the amount of snow and ice has diminished, sea level has risen and the concentration of carbon dioxide has increased to a level unprecedented in at least the last 800,000 years.”
The IPCC AR5 Synthesis report (PDF) claimed that the global temperature rise of >4°C combined with an increase in demand for food would "pose large risks to global food security."
Climate experts have been locked in talks with government bods for the past week.
"The science community has now spoken and is passing the baton to policymakers," said Pachauri.
On the projected changes in the climate system, the report authors said:
Surface temperature is projected to rise over the 21st Century under all assessed emission scenarios. It is very likely that heat waves will occur more often and last longer, and that extreme precipitation events will become more intense and frequent in many regions. The ocean will continue to warm and acidify, and global mean sea level to rise.
On climate change beyond 2100, it warned:
Many aspects of climate change and associated impacts will continue for centuries, even if anthropogenic emissions of greenhouse gases are stopped. The risks of abrupt or irreversible changes increase as the magnitude of the warming increases.
The IPCC added:
There are multiple mitigation pathways that are likely [panel's emphasis] to limit warming to below 2°C relative to pre-industrial levels. These pathways would require substantial emissions reductions over the next few decades and near zero emissions of CO2 and other long-lived GHGs by the end of the century.
Implementing such reductions poses substantial technological, economic, social, and institutional challenges, which increase with delays in additional mitigation and if key technologies are not available. Limiting warming to lower or higher levels involves similar challenges, but on different timescales.