Based on independent datasets, the content of the report was developed and peer-reviewed by experts affiliated with international and regional climate institutions and programs. Click through the following slides to learn more about the report's key findings.

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 recorded history, with the global surface temperature being .90°F ±0.18°F above the 1961–1990 average.

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

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

This “warm” Arctic, cold continents pattern is characteristic of the Arctic Oscillation's negative phase, and 2013 saw the most negative Arctic Oscillation on record in March. Similarly, a high-pressure pattern over Greenland and low pressure to the south re-emerged in late spring, causing cold Arctic air to surge into western and central Europe.

The southern hemisphere experienced warm temperature anomalies in both summer and winter. New Zealand, for example, experienced its warmest winter on record, and temperatures in parts of South America reached record-heights in the summer.

Rain, Snow and Ice

In 2013, global precipitation equaled the 1961-1990 averages according to the National Oceanic and Atmospheric Administration, but on the regional level, precipitation levels varied significantly.

Greenland, the southern Arabian Peninsula, central India and western China experienced wetter-than-average conditions, while it was 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 past few years. Eurasian snow cover, however, set a new record low for the month of May. June saw the second lowest snow cover across the hemisphere, second only to 2012.

For monitoring climate systems, soil moisture can be a key variable because it can influence the exchange of water and energy between the land surface and the atmosphere, WMO says. Wet soil conditions were noticeable, having impacts on floods in a number of regions in northeastern China, India, the Russian Federation, the Philippines and central Europe. Soil moisture anomalies indicated dryness in parts of the southern hemisphere, leaving Australia, South America and southern Africa to experience severe drought conditions 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 from the atmosphere. Since the industrial revolution, oceans have absorbed approximately one quarter of all carbon dioxide released into the atmosphere by humans.

The absorbed carbon dioxide forms a weak carbonic acid, causing ocean acidification. Ocean acidification is harming corals, shellfish and other marine life, and as the surface air temperatures rise, heat continues to be trapped in the Earth system as increased ocean heat content. According to the report, the ocean absorbed 93% of excess heat trapped in the Earth system between 1971 and 2010. Increased uptake results in changes in atmospheric and oceanic circulation patterns, particularly in the tropical Pacific regions.

Thermal expansion of the oceans and melting glaciers and ice caps have caused the global sea level to rise by 19 centimeters since the beginning of the 20th century, and WMO says preliminary analysis indicates the global average sea level reached a new record high in March 2013.

Some regions are experiencing a greater rise in sea level than others due to local variations in currents, land movements and ocean warming. The Pacific Ocean, specifically around the Philippines, has observed some of the highest rising sea level rates over the past 50 years. Much of this is due to the devastation caused by Typhoon Haiyan and the massive storm surge that followed.

Impacts on North America

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

Temperatures rebounded in the summer, and warmth extended into September. In Alaska, summer of 2013 was the second hottest on record, and October through December was the sixth warmest period on record for the state for that time period. Mexico also experienced record-high temperatures in July and August.

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

Drought conditions encompassed much of the central U.S. in 2012, the WMO says, but 2013 brought improvement. By the end of the year, about 31% of the country was experiencing drought, which was down from 61% in 2012. California, however, had its driest year since records began in 1895, with San Francisco receiving only 16% of its annual rainfall. In Colorado, scorching temperatures and strong winds contributed worst the worst wildfire in 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. each experienced late-winter storms, breaking state records. El Reno, Okla. was struck by a particularly powerful tornado in 2013, being the widest ever observed in the U.S.

Major Global Weather and Climate Events in 2013

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

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

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