On the move
1 Climate change is causing spring to come early in many parts of the world. In the US, for instance, spring was three weeks earlier than the average onset during the period from 1981 to 2010. Though an early end to winter may sound welcome, it can disrupt ecological systems, such as the link between flowers and the arrival of pollinating birds and insects.
2 The Arctic is undergoing exceptional changes. Overall, it is warming at twice the rate of the planet as a whole, resulting in record-low sea ice. In 2016, sea ice at the end of summer covered an area less than two-thirds of that at the end of the 20th century – a loss the equivalent of the area of the UK, Ireland, France, Spain, Germany and Italy put together. The huge Greenland Jakobshavn Glacier alone is retreating at about 0.6km a year.
3 Glacial melt from Greenland has led to a freshening of Arctic Ocean waters. This could lead to a disruption of the Atlantic meridional overturning circulation system – a key component of the global climate system – with huge implications for the North Atlantic climate.
4 Antarctica has the potential to contribute more than a metre of sea-level rise by 2100 – on top of the contribution to rising seas from other sources – and more than 15m over several centuries, if emissions continue unabated. Evidence suggests key glaciers, including Pine Island and Thwaites, may be in irreversible retreat.
5 Climate change has already increased the inflation-adjusted cost of damage from extreme storms and weather events from US$10 billion in the 1980s to US$50 billion in the past decade. Wildfires are also increasing. The number of blazes on public land in the western US has increased fivefold since the late 1970s, according to Californian wildfire expert LeRoy Westerling. Fires in Portugal last month killed more than 60 people, and fires are burning across huge areas of British Columbia, forcing 14,000 people from their homes.