The year 2013 tied 2007 as the sixth warmest year inrecorded history, and climate indicators show that the globe isexperiencing the impacts of climate change, a World MeteorologicalOrganization report says.

In its ”Statement on the Status of the Global Climate in2013,” the WMO says, “Although the climate varies naturally fromyear to year, it is clear that the planet is experiencing anoverall warming trend. Thirteen of the fourteen warmest years onrecord have all occurred in the 21st century, and each of thepast three decades has been warmer than the last, culminating with2001–2010 as the warmest decade on record.”

The report cites the Fifth Assessment Report of theIntergovernmental Panel on Climate Change, attributing steadywarming to the rising levels of greenhouse gases in theatmosphere.

The latest WMO report provides a snapshot of global andregional trends in weather and climate over the past year,highlighting some of the most significant and extreme weatherevents of 2013, drawing on input from leading researchinstitutions.

Based on independent datasets, the content of the report wasdeveloped and peer-reviewed by experts affiliated withinternational and regional climate institutions and programs. Clickthrough the following slides to learn more about the report's keyfindings.

The WMO is a specialized agency of the United Nations.

Read the full report here.

Temperatures

The year 2013 tied 2007 as the sixth-warmest year in recordedhistory, with the global surface temperature being .90°F ±0.18°Fabove the 1961–1990 average.

Temperature variability, the report indicates, is driven by thewarming El Niño and cooling La Niña. Neither of these weatherconditions were present in 2013, which was among the four warmestEl Niño-Southern Oscillation-neutral years on record.

The northern hemisphere's weather patterns in early 2013 wereinfluenced by Arctic Oscillation, bringing cooler-than-averagespring temperatures to much of Europe, southeastern United States,northwestern Russian Federation and parts of Japan. Meanwhile, theArctic region was considerably warmer than average, along withcentral and northern Africa, the eastern Mediterranean, southernRussian Federation and China.

This “warm” Arctic, cold continents pattern is characteristic ofthe Arctic Oscillation's negative phase, and 2013 saw the mostnegative Arctic Oscillation on record in March. Similarly, ahigh-pressure pattern over Greenland and low pressure to the southre-emerged in late spring, causing cold Arctic air to surge intowestern and central Europe.

The southern hemisphere experienced warm temperature anomaliesin both summer and winter. New Zealand, for example, experiencedits warmest winter on record, and temperatures in parts of SouthAmerica reached record-heights in the summer.

Rain, Snow and Ice

In 2013, global precipitation equaled the 1961-1990 averagesaccording to the National Oceanic and Atmospheric Administration,but on the regional level, precipitation levels variedsignificantly.

Greenland, the southern Arabian Peninsula, central India andwestern China experienced wetter-than-average conditions, while itwas unusually dry in the western United States, northern Canada,northern Siberia and Australia's eastern inland.

In North America, winter snow cover varied widely over the pastfew years. Eurasian snow cover, however, set a new record low forthe month of May. June saw the second lowest snow cover across thehemisphere, second only to 2012.

For monitoring climate systems, soil moisture can be a keyvariable because it can influence the exchange of water and energybetween the land surface and the atmosphere, WMO says. Wet soilconditions were noticeable, having impacts on floods in a number ofregions in northeastern China, India, the Russian Federation, thePhilippines and central Europe. Soil moisture anomalies indicateddryness in parts of the southern hemisphere, leaving Australia,South America and southern Africa to experience severe droughtconditions at the beginning of 2013.

Oceans

Oceans act as an effective buffer for the climate system,absorbing and storing large amounts of excess carbon and heat fromthe atmosphere. Since the industrial revolution, oceans haveabsorbed approximately one quarter of all carbon dioxide releasedinto the atmosphere by humans.

The absorbed carbon dioxide forms a weak carbonic acid, causingocean acidification. Ocean acidification is harming corals,shellfish and other marine life, and as the surface airtemperatures rise, heat continues to be trapped in the Earth systemas increased ocean heat content. According to the report, the oceanabsorbed 93% of excess heat trapped in the Earth system between1971 and 2010. Increased uptake results in changes in atmosphericand oceanic circulation patterns, particularly in the tropicalPacific regions.

Thermal expansion of the oceans and melting glaciers and icecaps have caused the global sea level to rise by 19 centimeterssince the beginning of the 20th century, and WMO sayspreliminary analysis indicates the global average sea levelreached a new record high in March 2013.

Some regions are experiencing a greater rise in sea level thanothers due to local variations in currents, land movements andocean warming. The Pacific Ocean, specifically around thePhilippines, has observed some of the highest rising sea levelrates over the past 50 years. Much of this is due to thedevastation caused by Typhoon Haiyan and the massive stormsurge that followed.

Impacts on North America

In 2013, temperatures across most of North America were aboveaverage, but more moderate than 2012. Winter, in general, waswarmer in the United States and Canada in 2013, although spring inthe contiguous United States was the coolest since 1996.

Temperatures rebounded in the summer, and warmth extended intoSeptember. In Alaska, summer of 2013 was the second hottest onrecord, and October through December was the sixth warmest periodon record for the state for that time period. Mexico alsoexperienced record-high temperatures in July and August.

It was also wetter than average in the United States, withMichigan and North Dakota experiencing record wet conditions.Alaska also observed its third wettest year on record, and thewettest year in the last half century.

Drought conditions encompassed much of the central U.S. in2012, the WMO says, but 2013 brought improvement. By the endof the year, about 31% of the country was experiencing drought,which was down from 61% in 2012. California, however, had itsdriest year since records began in 1895, with San Franciscoreceiving only 16% of its annual rainfall. In Colorado, scorchingtemperatures and strong winds contributed worst the worst wildfirein the state's history, according to the WMO.

Several parts of the U.S. were hit by late-season winter storms.Bismarck, N.D., Duluth, Minn., and Rapid City, S.D. eachexperienced late-winter storms, breaking state records. El Reno,Okla. was struck by a particularly powerful tornado in 2013, beingthe widest ever observed in the U.S.

Major Global Weather and Climate Events in2013

The report details the biggest global weather and climate eventsin 2013. Some of the major events include:

• Typhoon Haiyan devastated parts of the central Philippines, andis one of the strongest storms to ever make landfall
• Extreme precipitation led to severe floods in the Alps and inAustria, the Czech Republic, Germany, Poland and Switzerland.
• Israel, Jordan and the Syrian Arab Republic were struck byunprecedented snowfall.
• An extra-tropical windstorm affected several countries inwestern and northern Europe.
• Greenhouse gas concentrations in the atmosphere reached recordhighs.

For more details on climate events of 2013, read the full reporton the WMO's website.