Breaking records: UN report reviews major climate and weather events of 2012
The decline of Arctic sea ice in 2012 is a “clear and alarming sign of climate change” – that’s the verdict of a report today from the World Meteorological Organisation (WMO). The report, which investigates last year’s major climate and weather events, found 2012 was the 27th consecutive year with above average global temperature.
Top ten warmest year on record
Global average temperature in 2012 was 0.45 degrees Celsius warmer than the 1961 to 1990 long term average, according to the report. That’s the ninth warmest on record.
Natural climate fluctuations from year to year mean scientists don’t necessarily expect each year to be successively warmer than the last. The important point is that the world is significantly warmer than it was a few decades ago.
The years between 2001 and 2012 were among the top 13 warmest on record:
Image - Hottest Summers (note)The years 2001 to 2012 were among the warmest 13 on record. An Strong El Nino in 1998 made it an exceptionally warm year. Source: WMO Annual statement on the Status of the Global Climate in 2012
Secretary-General of the WMO, Michel Jarraud, explains:
“Although the rate of warming varies from year to year due to natural variability caused by the El Niño cycle, volcanic eruptions and other phenomena, the sustained warming of the lower atmosphere is a worrisome sign.”
“Disturbing signs”
The temperature of earth’s surface isn’t the only indicator of climate change. The report highlights how Arctic sea ice is diminishing rapidly due largely to rising global temperature – reaching a record low of 3.41 million square in summer 2012. Jarraud says:
“The record loss of Arctic sea ice in August-September – 18 per cent less than the previous record low of 2007 of 4.17 million square kilometres – was also a disturbing sign of climate change.”
Arctic sea ice in 2012 – and the next lowest extent in 2007 – compared to the 1979 to 2000 average. Source: WMO annual statement on the Status of the Global Climate in 2012.
The report highlights the consequences of rising temperatures for the Greenland ice sheet. In July 2012, 97 per cent of the ice sheet’s surface melted – the most in the 34-year satellite record.
The report also points out the slight increase in Antarctic sea ice, reaching a record high in March 2012. But satellite data show along with Greenland, Antarctica is losing mass overall.
Come rain or shine
Globally, rainfall was slightly higher in 2012 than the long term average for 1961 to 1990, according to the report. But the same pattern wasn’t experienced across the globe.
Much of the central United States, northern Mexico, northeastern Brazil, central Russia, and south-central Australia experienced drier-than-average weather. Northern Europe, western Africa, north-central Argentina, western Alaska, and most of northern China saw wetter than average conditions.
Snow cover also varied regionally. Winter in North America saw the fourth smallest snow cover on record, while the Eurasian continent experienced the fourteenth highest on record.
Extreme events
The image below from the report highlights the different types of extreme event experienced globally in 2012.
While the United States and south-east Europe experienced extreme drought, West Africa and Pakistan were hit by extreme flooding. Europe, northern Africa and Asia were affected by extreme cold and snow.
Significant global weather events in 2012. Source: WMO annual statement on the Status of the Global Climate in 2012.
The table below from the report highlights five of the most significant extreme events in 2012, alongside their estimated human and economic costs.
Topping the list is hurricane Sandy – which according to the report killed close to 230 people, caused major destruction and tens of billions of dollars in damage across the US and the Caribbean.
Source: WMO annual statement on the Status of the Global Climate in 2012.
Attributing a specific event to climate change is difficult as we can’t be certain whether it would have happened if the world wasn’t warming. But by increasing global temperatures, humans are changing the environment in which extreme events form. Jarraud explains:
“Natural climate variability has always resulted in such extremes, but the physical characteristics of extreme weather and climate events are being increasingly shaped by climate change.”
Determining if the frequency of tropical cyclones has changed beyond what we’d expect from natural variability is particularly difficult, mainly due to a lack of data around the world. The report points out that while the Atlantic basin experienced higher than average tropical cyclone activity, cyclone activity globally was close to average.
Some things can be expressed with more confidence, however. The report points out how rising sea levels are making low-lying coastal areas more vulnerable to flooding when a storm does reach landfall. Jarraud explains:
“[B]ecause global sea levels are now about 20 cm higher than they were in 1880, storms such as Hurricane Sandy are bringing more coastal flooding than they would have otherwise.”
Looking forward
By nature, extreme events are rare over the time period in which humans have been making measurements. But with global temperatures set to rise further this century, there is a lot of work still to be done to unravel the ways climate change is affecting their frequency and severity. Jarraud explains the sense of urgency in helping the most vulnerable countries to cope:
“Climate change is aggravating naturally occurring climate variability and has become a source of uncertainty for climate-sensitive economic sectors like agriculture and energy. It is vital that we continue to invest in the observations and research that will improve our knowledge about climate variability and climate change.”
The scientific messages carried in the report will be the main focus of the WMO’s executive council meeting when it convenes later this month.