13.11.2017 |

Climate change: Earth is approaching tipping points, warn scientists

Higher temperatures will result in yield losses (Photo: CC0)

As global temperatures continue to rise, Earth is approaching dangerous tipping points, leading scientists have warned. Future Earth and the Earth League, two international organizations representing sustainability scientists, have published the statement “The 10 Science ‘Must Knows’ on Climate Change” to provide support to negotiators at the COP23 climate conference. According to Hans Joachim Schellnhuber, director of the Potsdam Institute for Climate Impact Research, “some crucial climate-change facts tend to get lost in the noise of daily deliberations - even at an event such as the UN climate summit.” This is why the authors wish to “remind everyone of the very reason why ten thousands of people meet in Bonn: unprecedented risk to humanity due to global warming, as revealed by science.” Professor Johan Rockström, executive director of the Stockholm Resilience Centre and Chair of the Earth League, stressed that climate change caused by humans is no longer a future threat. “It has arrived, it is dangerous and it will get worse,” he said. “In the last two years evidence has accumulated that we are now on a collision course with tipping points in the Earth system,” he added. By crossing these thresholds, the planet may see abrupt, and possibly irreversible, shifts in the workings of the Arctic, Amazon, and other parts of the globe.

The ten points of the statement build on numerous international assessments and reports. The scientists warn that climate change will have a profound impact on human health by placing new pressures on the food and water security in nations around the world. “Accelerating changes in Earth’s natural systems are a significant threat to human health and livelihood as a result of possible impacts on nutrition, food availability, respiratory diseases, and the spread of parasites,” they say. For example, a recent estimate suggests that crop-yield losses could be 3-7% per degree of warming. By 2050, more than half of the world's population will live in water-stressed areas, and a billion or more will not have sufficient water. “These health threats will become increasingly severe over time without steps to reduce the risks. Areas with weak health infrastructure, mostly in developing countries, will be the least able to cope without assistance to prepare for and respond to health emergencies. Another issue mentioned in the statement is that climate change is likely to exacerbate migration, civil unrest and even conflict. In 2015, more than 19 million people globally were displaced by natural disasters and extreme weather events, and climate change will likely cause that number to grow.

Point 8 on the list is a call to action: “The world needs to act fast: If humans continue to emit greenhouse gases at current rates, the remaining carbon budget to reduce risk of exceeding the 2 degrees Celsius target will be exhausted in around 20 years. Emissions should peak by 2020 and approach zero by around 2050 if the world is serious about reducing risk.” This must also be done in concert with halting deforestation, turning agriculture from carbon source to carbon sink, and protecting existing carbon sinks on ocean and land, the document says. But even if the world meets the Paris Agreement targets, communities across the globe will still need to build resilience and adapt to the changes already under way. “Even keeping temperature rise to below 2 °C above pre-industrial levels, some regions will experience increased risks of rising sea levels, forest fires, and water and food insecurity and may see increases in extreme heat, disease, and weather events,” the authors write. Safeguarding and strengthening the resilience of natural systems, from forests to soils to oceans, as the climate warms will therefore require a global transformation to sustainability. “The cumulative scientific evidence indicates that sustainable development, with transformations to sustainable food systems, decarbonised energy systems, resilient cities, human equity and justice, universal health and education, eradicated poverty and hunger, sustainable consumption and production, healthy oceans, safe water, and protected biodiversity, form a fundamental cornerstone for success in achieving good climate adaptation and climate resilience,” the scientists conclude. (ab)

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