Annual global surface temperatures passed the both important and symbolic threshold of 1°C above pre-industrial levels for the first time last year.
Governments pledged in the Paris Agreement in December 2015 to aim to limit the global temperature increase to 1.5°C above pre-industrial levels.
Long-term warming and ‘one of the strongest El Niňo events the globe has experienced since at least 1950’ both contributed to the record temperature, says the report.
The study, based on contributions from 450 scientists working in 62 counties, gives a detailed update on global climate indicators from environmental monitoring stations on land, water, ice and in space. These indicators point to both the causes and effects of a warming planet.
As well as the record global surface temperature in 2015, 0.1°C above 2014’s previous record, greenhouse gas emissions in 2015 were the highest on record. Carbon dioxide, methane and nitrous oxide emissions all rose to new record highs during the year. The annual average atmospheric carbon dioxide concentration at Mauna Loa, Hawaii (the local of the world’s longest direct time series of carbon dioxide measurements), was 400.8 parts per million (ppm), surpassing 400 ppm for the first time. The 3.1 ppm increase on 2014 was the largest annual increase observed in the 58-year record.
Globally average sea surface temperatures in 2015 were also the highest on record. El Niňo warmed the eastern equatorial Pacific and the north-east Pacific remained anomalously warm, while the North Atlantic remained colder than average.
The report also found that the global upper ocean heat content was the highest recorded, reflecting the continuing accumulation of thermal energy in the upper layer of the oceans. The global average sea level was, again, the highest on record, at around 70 mm higher than the 1993 average (marking the start of the satellite altimeter record).
Meanwhile an increase in the water cycle saw enhanced precipitation variability; the maximum sea ice extent in February 2015 was the smallest on record; tropical cyclone occurrences continued to be above average; and 2015 was the 36th consecutive year of overall alpine glacier retreat across the globe.
‘When we think about being climate resilient, both [short and long] time scales are important to consider, ‘ says Thomas R Karl, Director of the NOAA National Centers for Environmental Information. ‘Last year’s El Niňo was a clear reminder of how short-term events can amplify the relative influence and impacts stemming from longer-term global warming trends.’
Meanwhile, and as El Niňo fades, in 2016 records are still being set in the form of continuing monthly average temperature records, and as a result 2016 is already thought to best 2015 as the hottest year ever recorded – according to a mid-year analysis from NASA.
So far on average the 2016 temperate has been 1.3°C above pre-industrial levels. July 2016 marked the 15th consecutive record-breaking month for global temperature. NASA confirmed that it was not just the warmest July ever recorded, but the warmest month ever recorded in history.