The increasingly visible human footprint on extreme weather and climate events with dangerous and costly impacts is evident in a detailed analysis of the global climate 2011-2015 – the hottest five-year period on record, by the World Meteorological Organisation (WMO).
The record temperatures were accompanied by rising sea levels and declines in Arctic sea-ice extent, continental glaciers and northern hemisphere snow cover. All these climate change indicators confirmed the long-term warming trend caused by greenhouse gases. Carbon dioxide reached the significant milestone of 400 parts per million in the atmosphere for the first time in 2015, according to the WMO report submitted to the UN climate change conference.
The 2011-2015 period was the warmest five-year period on record globally and for all continents apart from Africa (second warmest). Temperatures for the period were 0.57 °C above the average for the standard 1961–1990 reference period. The warmest year on record to date was 2015, during which temperatures were 0.76 °C above the 1961–1990 average, followed by 2014. The year 2015 was also the first year in which global temperatures were more than 1 °C above the pre-industrial era.
The Global Climate 2011-2015 also examines whether human-induced climate change was directly linked to individual extreme events. Of 79 studies published by the Bulletin of the American Meteorological Society between 2011 and 2014, more than half found that human-induced climate change contributed to the extreme event in question. Some studies found that the probability of extreme heat increased by 10 times or more.
The Paris Agreement aims at limiting the global temperature increase to well below 2 ° Celsius and pursuing efforts towards 1.5 ° Celsius above pre-industrial levels. “This report confirms that the average temperature in 2015 had already reached the 1°C mark,” said WMO Secretary-General Petteri Taalas, who predicted that even that record is likely to be beaten in 2016.
As pointed out by the WMO official, the effects of climate change have been consistently visible on the global scale since the 1980s: rising global temperature, both over land and in the ocean; sea-level rise; and the widespread melting of ice. It has increased the risks of extreme events such as heatwaves, drought, record rainfall and damaging floods.
The report highlighted some of the high-impact events. These included the East African drought in 2010-2012 which caused an estimated 258,000 excess deaths and the 2013-2015 southern African drought; flooding in South-East Asia in 2011 which killed 800 people and caused more than US$40 billion in economic losses, 2015 heatwaves in India and Pakistan in 2015, which claimed more than 4,100 lives; Hurricane Sandy in 2012 which caused US$67 billion in economic losses in the US, and Typhoon Haiyan which killed 7,800 people in the Philippines in 2013.
The report was submitted to the Conference of the Parties of the United Nations Framework Convention on Climate Change. The five-year timescale allows a better understanding of multi-year warming trends and extreme events such as prolonged droughts and recurrent heatwaves than an annual report. Today (Nov 14) WMO will release its provisional assessment of the state of the climate in 2016 to inform the climate change negotiations in Marrakech, Morocco.