2015 likely to be warmest on record, 2011-2015 warmest 5-year period: WMO

the seasonal cycle. In 2015, the daily maximum extent, which occurred on 25 February 2015, was the lowest on record at 14.54 million km². The minimum sea ice extent was on 11 September when the extent was 4.41 million km², the fourth lowest in the satellite record.

In the southern hemisphere, the daily maximum extent of 18.83 million km² was recorded on 6 October in Antarctica. This is the 16th highest maximum extent in the satellite record. The minimum extent, recorded on 20 February, was 3.58 million km², the 4^th highest on record.

Climate change attribution
Scientific assessments have found that many extreme events in the 2011-2015 period, especially those relating to extreme high temperatures, have had their probabilities over a particular time period substantially increased as a result of human-induced climate change — by a factor of 10 or more in some cases.

Of seventy-nine studies published by the Bulletin of the American Meteorological Society between 2011 and 2014, more than half found that anthropogenic climate change contributed to extreme events. The most consistent influence has been on extreme heat, with some studies finding that the probability of the observed event has increased by 10 times or more.

Examples include the record high seasonal and annual temperatures in the United States in 2012 and in Australia in 2013, hot summers in eastern Asia and western Europe in 2013, heatwaves in spring and autumn 2014 in Australia, record annual warmth in Europe in 2014, and the Argentine heatwave of December 2013.

Some longer-term events, which have not yet been the subject of formal attribution studies, are consistent with projections of near- and long-term climate change. These include increased incidence of multi-year drought in the subtropics, as manifested in the 2011-2015 period in the southern United States, parts of southern Australia and, towards the end of the period, southern Africa. There have also been events, such as the unusually prolonged, intense and hot dry seasons in the Amazon basin of Brazil in both 2014 and 2015 which, while they cannot yet be stated with confidence to be part of a long-term trend, are of considerable concern in the context of potential “tipping points” in the climate system as identified by the Intergovernmental Panel on Climate Change.

The WMO notes that its reports on the Status of the Global Climate are based on contributions from WMO’s 191 Members. The global temperature analysis is principally derived from three complementary datasets maintained by the Hadley Centre of the U.K.’s Met Office and the Climatic Research Unit, University of East Anglia, United Kingdom (combined); the U.S. National Oceanic and Atmospheric Administration (NOAA) National Centers for Environmental Information; and the Goddard Institute of Space Studies (GISS) operated by the National Aeronautics and Space Administration (NASA). Global average temperatures are also estimated using reanalysis systems, which use a weather forecasting system to combine many sources of data to provide a more complete picture of global temperatures. WMO uses data from the reanalysis produced by the European Center for Medium-Range Weather Forecasts and the Japan Meteorological Agency.

— See also: The WMO Bulletin on Greenhouse Gas Concentrations is available here; information about the ongoing El Niño event is available here, and an animation here; WMO has released a new series of its Weather Reports for the Future, with television presenters from around the world giving a weather report from the year 2050, based on possible climate change scenarios.