Planet has 'already reached climate change tipping points'
Nine key 'tipping points' that will lead to catastrophic global warming have been reached, a group of leading scientists have warned. Scientists say that in these areas sufficient damage has been done that the effects of global warming could accelerate and create a 'cascade' effect. Because tipping points have been crossed, it could lead to a domino effect, accelerating global warming impacts, threatening human existence, scientists warn. 'The situation is urgent and we need an emergency response', said said Tim Lenton, head of the University of Exeter team behind this study. 'The growing threat of rapid, irreversible changes means it is no longer responsible to wait and see what happens.' In the journal Nature, the scientists said urgent action was needed to reduce greenhouse gas emissions - as other key tipping points, that have not yet been activated could soon be hit. Other tipping points not currently activated include heating up of deep water in the Antarctic, and the release of methane stored in the Ocean in polar regions. They also identified a reduction in rainfall in the Indian monsoon, and a major loss of oxygen in the ocean as potential areas of risk. Professor Lenton said: 'A decade ago we identified a suite of potential tipping points in the Earth system, now we see evidence that over half of them have been activated.' His co-author Johan Rockstrom, of the Potsdam Institute for Climate Impact Research, said it was not only human pressures on Earth that continue to rise at unprecedented levels. 'It is also that as science advances, we must admit that we have underestimated the risks of unleashing irreversible changes, where the planet self-amplifies global warming. 'This is what we now start seeing, already at 1C global warming. 'Scientifically, this provides strong evidence for declaring a state of planetary emergency, to unleash world action that accelerates the path towards a world that can continue evolving on a stable planet.' The collapse of major ice sheets on Greenland, West Antarctica and part of East Antarctica would result in around 10 metres of irreversible sea-level rise. Despite most countries having signed the Paris Agreement, pledging to keep global warming well below 2C, current national emissions pledges - even if they are met - would lead to 3C of warming. Although future tipping points and the interplay between them is difficult to predict, the scientists argue: 'If damaging tipping cascades can occur and a global tipping cannot be ruled out, then this is an existential threat to civilisation. 'No amount of economic cost-benefit analysis is going to help us. We need to change our approach to the climate problem.' Professor Lenton added: 'We might already have crossed the threshold for a cascade of inter-related tipping points. 'However, the rate at which they progress, and therefore the risk they pose, can be reduced by cutting our emissions.' Though global temperatures have fluctuated over millions of years, the authors say humans are now 'forcing the system'. 'With atmospheric carbon dioxide concentration and global temperature increasing at rates that are an order of magnitude higher than at the end of the last ice age.' Will Steffen professor of climate and Earth system science at the Australian National University said the study shows two of the tipping points - coral reefs and Arctic sea ice - may have already been tipped. 'The consequence of activating such a cascade would be an unstoppable slide into hothouse Earth conditions. 'The schoolchildren are right - we indeed have a climate emergency, and an emergency-level response is now needed to ensure that we don't activate the tipping cascade.' The research has been published in the journal .