Summary


Although still a preliminary assessment covering only the first nine months of 2013, this WMO report provides a comprehensive coverage of global and regional land and sea temperatures and gives associated detail on Arctic, Greenland and Antarctic ice with notes on sea level rise and atmospheric greenhouse gases which are key indicators of global warming. The report also covers regional precipitation and climatic extremes including high temperatures / heat waves, drought, wildfires, precipitation events and floods, snow and extreme cold, and storms, cyclones / typhoons and hurricanes.

The WMO expects 2013 to be one of the ten warmest years since the beginning of global records in 1850. The first nine months equal 2003 as seventh warmest on record with a combined global (land and sea) temperature almost half a degree (0.48°C ± 0.12°C) above the 1961-1990 average.


Land temperatures


The global land temperature for 2013 has equaled 2012 as the sixth warmest on record at 0.80°C above the 1961−1990 average.

The distribution of highest anomalous temperature varies geographically. For example, record high land temperatures were recorded in the USA in 2012 and in Australia in 2013. The Australian Bureau of Meteorology has reported that the summer of 2012-13 was the hottest on record in Australia with, nationally, the hottest day ever recorded and a record seven consecutive days with maximum temperature over 39°C for the nation as a whole. Record high temperatures were widespread (e.g. both Sydney and Hobart experienced their hottest day since the commencement of recording).

Temperature Anomalies 2013
Temperature Anomalies 2013


There has been considerable geographic as well as seasonal variation in temperatures throughout 2013. The extent and import of climatic variability is clearly demonstrated in the WMO report. North America has been above average although not to the 2012 extremes. However, the contiguous USA had its coolest spring since 1996 while Alaska had its second warmest summer on record. At some localities in Argentina, maximum and minimum records were exceeded within a few days of each other in August and September. Many daily maximum records were exceeded in South Asia and Japan had its hottest summer on record. Record temperatures were recorded at locations in South Africa and Ghana, Pakistan, Austria and Japan and most of southern China experienced a long and severe heat wave.


Sea-surface temperatures – ENSO and the Arctic oscillation


Variations in sea surface temperatures in the equatorial zone of the Pacific Ocean, coupled with variations in surface air pressure influence atmospheric circulation and affect ocean currents and have a widespread (even global) effect on weather—notably on temperature and rainfall patterns. Phenomena related to equatorial pacific sea surface temperature variations are described as being related to the ENSO cycle.

ENSO stands for El Niño/Southern Oscillation. This is an oscillation between El Niño conditions (periodic sea-surface warming), and La Niña conditions (periodic sea-surface cooling). The WMO notes that ENSO-neutral conditions have prevailed since April 2012. Despite this, the oceans south of Australia and the equatorial western Pacific Ocean have been exceptionally warm and the global ocean surface temperature for the nine months to September 2013 equals 2004 as the sixth warmest on record, at 0.35°C above the 1961−1990 average.

Typical Warm Phase ENSO Dec-Feb
Typical Warm Phase ENSO Dec-Feb
Typical Warm Phase ENSO Jun-Aug
Typical Warm Phase ENSO Jun-Aug


Typical Cool Phase ENSO Dec-Feb
Typical Cool Phase ENSO Dec-Feb
Typical Cool Phase ENSO Jun-Aug
Typical Cool Phase ENSO Jun-Aug


There is an important relationship between ENSO variability, the incidence of extreme wet and dry conditions and the effects of weather extremes on human health, safety and food supplies. A recent scientific report by Doi et al has confirmed that a coastal oceanic warm event, named the Ningaloo Niño, can be predicted two seasons ahead and, used with an ocean-atmosphere general circulation model, successfully predicted the unprecedented oceanic warmth off the Western Australia coast in February 2011.

In addition to ENSO, global weather patterns—and therefore global average temperatures—are affected by other naturally occurring oscillations. One of these is the Arctic Oscillation and the WMO report describes variations attributable to its characteristics in 2013.


The “Arctic Oscillation” is a pattern of differential atmospheric pressure between the Arctic and mid-latitudes in the Northern Hemisphere. High atmospheric pressure in the Arctic with low pressure in the mid-latitudes is called the ‘negative phase’ with the opposite pattern in its ‘positive phase’. The negative phase prevailed in early 2013. It had an extreme effect on temperatures in some regions for part of the year. While higher than average temperatures prevailed in the arctic and many land areas, in particular Australia, the Spring months in much of Europe, the southeastern USA and some other areas were cooler than average with several ‘frigid polar air outbreaks’.

Arctic Oscillation
Arctic Oscillation


Left: Effects of the Positive Phase of the Arctic Oscillation. Right: Effects of the Negative Phase of the Arctic Oscillation. —Credit: J. Wallace, University of Washington. Source : US National Snow and Ice Data Centre


Ice sheets and sea ice


For more detailed information on changes in the distribution and volume of ice see our article on IPCC AR5 - A new assessment of the Cryosphere.

The WMO report explains the effect of melting sea ice in reducing reflection of sunlight and increasing its absorption by the ocean and states that the ‘decline of sea ice in the Arctic Ocean in the past three decades is largely attributed to global warming’. Maximum sea ice extent in March 2013 was half a million sq km less than the 1981-2010 March average. Its minimum extent in September was the sixth smallest on record reflecting an average decadal rate of decrease of 13.7%. The WMO also cites University of Colorado findings that coverage of ice four years and older has decreased markedly from 18% in 1984 to 3% in 2013.

In contrast, Antarctic sea ice extent reached a record maximum in September, consistent with a decadal average rate of increase of 1.15%. While the mechanism(s) underlying the increase in Antarctic sea ice remains an open question, it is considered likely to reflect changing atmospheric circulation and, possibly, other factors including changing ocean circulation. A report by the Antarctic Climate and Ecosystem Cooperative Research Centre confirms that changes in the characteristics of Antarctic sea ice significantly alter ocean-atmosphere interaction, ocean circulation, and ecological variables ACECRC . Research is continuing to clarify feedback mechanisms operating in the Antarctic.

Sea Ice Extent
Sea Ice Extent


Rising sea levels


The IPCC states that the rate of global average sea level rise throughout the 20th Century has been in the range 1.0 to 2.0 mm/yr. Noting that sea level records show that it has been rising at an average rate of 3.2 ±0.4 mm/yr since 1993, the WMO report confirms that global sea level reached a new record high during March 2013.

Sea Level Rise
Sea Level Rise


Other Climatic Extremes


Severe drought conditions were experienced in Brazil, the Marshall Islands, New Zealand, China, Angola and Namibia with serious effects on water and food supplies. Wildfires had devastating effects in the USA and Australia. There was major and widespread flooding from extreme rainfall events in eastern Australia, Africa, Argentina, Switzerland, Germany, Poland, Austria and the Czech Republic, in northern India and Nepal, northern China and eastern Russia, and in the USA (Colorado). Exceptional snowfalls affected parts of Spain, the UK and Latvia.

Although major storm events (cyclones / typhoons, hurricanes etc) in the year 2013 have been near or below average, there have been several exceptional events since the end of September – most notably affecting the Philippines and the Bay of Bengal region of the North Indian Ocean, but also China (especially Taiwan and Hong Kong), Mexico, Vietnam and Cambodia. Tornados in the USA (Oklahoma) caused deaths and massive damage, while France experienced its strongest tornado for 5 years.

Typhoon Haiyan
Typhoon Haiyan

Super Typhoon at Philippines landfall

Main article source : WMO Provisional Statement on Status of the Climate in 2013 (WMO)