Observed global climate change

The US National Oceanic and Atmospheric Administration’s (NOAA) Climate.gov website has a dashboard with global climate information (including information on recently observed changes) to support informed decision-making, including recently observed changes.

NOAA's observations on global climate from its State of the Climate in 2013 report, include:

  • Greenhouse gases continued to climb: Concentrations of major greenhouse gases concentrations, including carbon dioxide (CO2), methane and nitrous oxide, continued to rise during 2013, once again reaching historic high values. Atmospheric CO2 concentrations increased by 2.8 ppm in 2013, reaching a global average of 395.3 ppm for the year.
  • Warm temperature trends continued near the Earth’s surface: Four major independent datasets showed that 2013 was among the warmest years on record, ranking between second and sixth, depending upon the dataset used. In the Southern Hemisphere, Australia observed its warmest year on record, Argentina had its second warmest and New Zealand its third warmest.
  • Sea- surface temperatures increased: Four independent datasets indicated that the globally averaged sea surface temperature for 2013 was among the 10 warmest on record.
  • Sea level continued to rise: Global mean sea level continued to rise during 2013, on pace with a trend of 3.2 ± 0.4 mm per a year over the past two decades.
  • The Arctic continued to warm and the sea ice extent remained low: The Arctic observed its seventh warmest year since records began in the early 20th century. Arctic sea ice extent was the sixth lowest since satellite observations began in 1979. All seven lowest sea ice extents on record have occurred in the past seven years.
  • Antarctic sea ice extent reached a record high for the second year in a row and the; South Pole station set a record high temperature: The Antarctic maximum sea ice extent reached a record high of 7.56 million square miles on 1 October 2013. This was 0.7 per cent higher than the previous record high extent of 7.51 million square miles (that occurred in 2012) and 8.6 per cent higher than the record low maximum sea ice extent of 6.96 million square miles that occurred in 1986. Near the end of the year, the South Pole had its highest annual temperature since records began in 1957.

Intergovernmental Panel on Climate Change (IPCC)

The Intergovernmental Panel on Climate Change (IPCC), formed by the World Meteorological Organisation and the United Nations Environment Programme, reviews the scientific evidence for climate change and summarises these findings in regular assessment reports.

The IPCC started releasing information from its Fifth Assessment Report (AR5) in September 2013. The IPCC Working Group I assesses the physical scientific components of the climate system and climate change, including changes in greenhouse gases in the atmosphere; and observed changes in air, land and ocean temperatures, rainfall, glaciers and ice sheets, and sea and ocean levels. A ‘Summary for Policymakers’ contains the major findings from the Working Group I report. These include:

  • Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia. The atmosphere and ocean have warmed, the amounts of snow and ice have diminished, sea level has risen, and the concentrations of greenhouse gases have increased.
  • Total radiative forcing is positive and has led to an uptake of energy by the climate system. The largest contribution to total radiative forcing is caused by the increase in the atmospheric concentration of CO2 since 1750.
  • Human influence on the climate system is clear. This is evident from the increasing greenhouse gas concentrations in the atmosphere, positive radiative forcing, observed warming, and understanding of the climate system.
  • Continued emissions of greenhouse gases will cause further warming and changes in all components of the climate system. Limiting climate change will require substantial and sustained reductions of greenhouse gas emissions.

The reports of Working Groups II - Impacts, Adaptation and Vulnerability - and III – Mitigation of Climate Change were released in March and April 2014, and the Synthesis Report released on 31 October 2014.

Climate change trends

The IPCC has this to say about earlier periods of change in Earth’s history:

Climate has changed on all time scales throughout Earth’s history. Some aspects of the current climate change are not unusual, but others are. The concentration of CO2 in the atmosphere has reached a record high relative to more than the past half-million years, and has done so at an exceptionally fast rate. Current global temperatures are warmer than they have ever been during at least the past five centuries, probably even for more than a millennium. If warming continues unabated, the resulting climate change within this century would be extremely unusual in geological terms. Another unusual aspect of recent climate change is its cause: past climate changes were natural in origin (see FAQ 6.1), whereas most of the warming of the past 50 years is attributable to human activities.
Extract from (Solomon S., Qin D., Manning M., Chen Z., Marquis M., Averyt K.B., Tignor M., Miller H.L. (eds) ‘2007 Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change’, Cambridge University Press, Cambridge, United Kingdom].

Visit the IPCC’s FAQ entitled Is the Current Climate Change Unusual Compared to Earlier Changes in Earth’s History for more information.