Severe droughts and heatwaves, thought to be largely the result of human-induced global warming have combined with the natural El Nino phenomenon to produce the warmest year ever recorded, meteorologists say.
In its annual report, The State of the Global Climate, the World Meteorological Organization (WMO) made it clear on Monday that 2015 was an exceptional year in the planet’s climatological history.
The year was the warmest year since 1850. Most of this was due to greenhouse gas emissions, the WMO said, while the El Nino, one of the strongest in the past half century, made a minor contribution.
There were some differences in temperature over land and over the sea surface, but combined, 2015 was 0.76C above the 1960-1990 average, and a full 1C above the 1850-1900 average.
It was a particularly warm year across Europe, Eurasia, South America, Africa, the Middle East and the western United States.
Both the Russian Federation and China had their warmest years on record, and in most European countries it was either the warmest or one of the top three warmest years on record.
The exception to this warming trend was in Antarctica, where strong westerly winds, part of a natural flux, resulted in cooling over eastern Antarctica and a warming over the Antarctic Peninsula.
In any given year, precipitation is always highly variable, both at a regional and local level, and the WMO’s report found that 2015 was no exception, although some definite trends are apparent.
Unusually high rainfall was recorded across the southern US, Mexico and much of central and northern South America, as well as much of Asia, including Pakistan and Afghanistan.
Dry areas included Central America, northeastern South America, central and southern Europe, Southeast Asia and Southern Africa.
The El Nino helped to warm the central and eastern Pacific by 1C, (although its overall contribution to global temperatures is thought to be no more than 0.1 to 0.2C). Partly as a result of thermal expansion, global sea levels are now 45mm above 2004 levels and are rising at a greater rate than at any time since the early 1990s.
Arctic sea ice has been disappearing year-on-year since reliable satellite data became available in the 1970s. In 2015, the maximum ice extent, on February 25, was the lowest on record. The minimum ice extent on September 11 was the fourth lowest on record.
The report also makes mention of the remarkable warming which took place in the Arctic in late December. On December 30, the temperature at the North Pole was 0.7C, at least 35C above average.
The picture in Antarctica is much less clear, and there was no discernible pattern in the ice extent, perhaps suggesting that we have a long way to go to fully understanding the climatology of this region.
Analysis of greenhouse gases, responsible for much of the current warming, shows that carbon dioxide levels are now 43 percent above pre-industrial levels.
Preliminary data for 2015 shows that the annual increase of 3.01 parts per million, per year, was a record. Atmospheric carbon dioxide has now passed the 400 parts per million level.
Methane, another very powerful, but shorter-lived, greenhouse gas also reached a record high.
Twenty years ago, the depletion of ozone in the upper atmosphere was a subject much in the news. The ozone “hole” was a result of the use of refrigerant gases which destroyed the ozone, allowing harmful ultraviolet radiation to penetrate to the surface, producing an elevated cancer risk.
The reduction in the use of these gases following the Montreal Protocol was a shining example of what might be achieved with international cooperation and legislation.
Unfortunately, the compounds already in the atmosphere will take decades to disperse. In the meantime, the report found that the ozone hole was the joint second largest on record.
Much of the report makes depressing reading for those worried about the state of our planet. This is especially so as 2016 is already shaping up to be an even warmer year than 2015, with global temperatures rising at an alarming rate.
The report does highlight the Paris Agreement of December 2015 which set out to limit temperature rises to less than 2C above pre-industrial limits, with a target of 1.5C.
Some of the “outstanding” events of 2015, as highlighted in the report, included:
Africa: The second warmest year since 2010.
India and Pakistan: A 47C heatwave in May killed 2,500 in India, while a June heatwave resulted in the deaths of 1,600 in Pakistan.
Yemen: Cyclone Chapala became the first hurricane-strength storm to make landfall.
Morocco: Thirteen times the average monthly rainfall total fell in Marrakech in only one hour on August 6.
Mexico: Recorded the wettest March since 1941. The country was also hit by Hurricane Patricia, the second strongest cyclone (after Super Typhoon Haiyan) ever recorded. Winds were as high as 346km/h.
Eastern North Pacific: The first time three major hurricanes were observed simultaneously since records began in 1949.