The Climate Change Portal
Average surface air temperatures from 2011 to 2020 compared to the 1951-1980 average. Source: NASA
Climate change includes both global warming driven by human-induced emissions of greenhouse gases and the resulting large-scale shifts in weather patterns. Though there have been previous periods of climatic change, since the mid-20th century humans have had an unprecedented impact on Earth's climate system and caused change on a global scale.
The largest driver of warming is the emission of gases that create a greenhouse effect, of which more than 90% are carbon dioxide (CO
2) and methane. Fossil fuel burning (coal, oil, and natural gas) for energy consumption is the main source of these emissions, with additional contributions from agriculture, deforestation, and the chemical reactions in certain manufacturing processes. The human cause of climate change is not disputed by any scientific body of national or international standing. Temperature rise is amplified by climate feedbacks, such as loss of sunlight-reflecting snow and ice cover, increased water vapour (a greenhouse gas itself), and changes to land and ocean carbon sinks.
On land, where temperatures have risen about twice as fast as the global average, deserts are expanding and heat waves and wildfires are becoming more common. Temperature rise is also amplified in the Arctic, where it has contributed to melting permafrost, glacial retreat and sea ice loss. Warmer temperatures are increasing rates of evaporation, causing more intense storms and weather extremes. Impacts on ecosystems include the relocation or extinction of many species as their environment changes, most immediately in coral reefs, mountains, and the Arctic. Climate change threatens people with food insecurity, water scarcity, flooding, infectious diseases, extreme heat, economic losses, and displacement. These human impacts have led the World Health Organization to call climate change the greatest threat to global health in the 21st century. Even if efforts to minimise future warming are successful, some effects will continue for centuries, including rising sea levels, rising ocean temperatures, and ocean acidification.
Many of these impacts are already felt at the current level of warming, which is about 1.2 °C (2.2 °F). The Intergovernmental Panel on Climate Change (IPCC) has issued a series of reports that project significant increases in these impacts as warming continues to 1.5 °C (2.7 °F) and beyond. Additional warming also increases the risk of triggering critical thresholds called tipping points. Responding to these impacts involves both mitigation and adaptation. Mitigation – limiting climate change – consists of reducing greenhouse gas emissions and removing them from the atmosphere. Methods to achieve this include the development and deployment of low-carbon energy sources such as wind and solar, a phase-out of coal, enhanced energy efficiency, and forest preservation. Adaptation consists of adjusting to actual or expected climate, such as through improved coastline protection, better disaster management, and the development of more resistant crops. Adaptation alone cannot avert the risk of "severe, widespread and irreversible" impacts.
Under the 2015 Paris Agreement, nations collectively agreed to keep warming "well under 2.0 °C (3.6 °F)" through mitigation efforts. However, with pledges made under the Agreement, global warming would still reach about 2.8 °C (5.0 °F) by the end of the century. Limiting warming to 1.5 °C (2.7 °F) would require halving emissions by 2030 and achieving near-zero emissions by 2050. (Full article...)
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This image shows the Arctic as observed by the Advanced Microwave Scanning Radiometer for EOS (AMSR-E) aboard NASA’s Aqua satellite on September 16, 2007. The image denotes a record sea ice
minimum in the Arctic.
In the news
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Walter Heinrich Munk (October 19, 1917 – February 8, 2019) was an American physical oceanographer. One of the first scientists to bring statistical methods to the analysis of oceanographic data, Munk is noted for creating fruitful areas of research that continue to be explored by other scientists. Munk's work garnered him many prestigious awards including the National Medal of Science, the Kyoto Prize, and induction to the French Legion of Honour.
Munk worked on a wide range of topics, including surface waves, geophysical implications of variations in the Earth's rotation, tides, internal waves, deep-ocean drilling into the sea floor, acoustical measurements of ocean properties, sea level rise, and climate change. Beginning in 1975, Munk and Carl Wunsch developed ocean acoustic tomography, to exploit the ease with which sound travels in the ocean and use acoustical signals for measurement of broad-scale temperature and current. In a 1991 experiment, Munk and his collaborators investigated the ability of underwater sound to propagate from the Southern Indian Ocean across all ocean basins. The aim was to measure global ocean temperature. The experiment was criticized by environmental groups, who expected that the loud acoustic signals would adversely affect marine life. Munk continued to develop and advocate for acoustical measurements of the ocean throughout his career.
Munk's career began before the outbreak of World War II and ended nearly 80 years later with his death in 2019. The war interrupted his doctoral studies at the Scripps Institution of Oceanography
(Scripps), and led to his participation in U.S. military research efforts. Munk and his doctoral advisor Harald Sverdrup
developed methods for forecasting wave conditions which were used in support of beach landings in all theaters of the war. He was involved with oceanographic programs during the atomic bomb tests in Bikini Atoll
. For most of his career, he was a professor of geophysics
at Scripps at the University of California
in La Jolla
. Additionally, Munk and his wife Judy
were active in developing the Scripps campus and integrating it with the new University of California, San Diego
. Munk's career included a number of prestigious positions, including being a member of the JASON think tank
, and holding the Secretary of the Navy/Chief of Naval Operations Oceanography Chair. (Full article...
The following are images from various climate-related articles on Wikipedia.
Carbon dioxide in Earth's atmosphere)
Carbon Dioxide observations from 2005 to 2014 showing the seasonal variations and the difference between northern and southern hemispheres (from
2 flows from anthropogenic sources (left) into Earth's atmosphere, land, and ocean sinks (right) since year 1960. Units in equivalent gigatonnes carbon per year. (from Carbon dioxide in Earth's atmosphere)
standard deviation (horizontal axis). According to Hansen et al. (2012), the distribution of anomalies has shifted to the right as a consequence of global warming, meaning that unusually hot summers have become more common. This is analogous to the rolling of a dice: cool summers now cover only half of one side of a six-sided die, white covers one side, red covers four sides, and an extremely hot (red-brown) anomaly covers half of one side. (from Attribution of recent climate change)
Frequency of occurrence (vertical axis) of local June–July–August temperature anomalies (relative to 1951–1980 mean) for Northern Hemisphere land in units of local
History of climate change science)
Mean temperature anomalies during the period 1965 to 1975 with respect to the average temperatures from 1937 to 1946. This dataset was not available at the time. (from
Temperature record of the last 2,000 years)
Global average temperatures show that the Medieval Warm Period was not a planet-wide phenomenon, and that the Little Ice Age was not a distinct planet-wide time period but rather the end of a long temperature decline that preceded recent global warming. (from
Atmospheric gases only absorb some wavelengths of energy but are transparent to others. The absorption patterns of water vapor (blue peaks) and carbon dioxide (pink peaks) overlap in some wavelengths. Carbon dioxide is not as strong a greenhouse gas as water vapor, but it absorbs energy in longer wavelengths (12–15 micrometers) that water vapor does not, partially closing the "window" through which heat radiated by the surface would normally escape to space. (Illustration NASA, Robert Rohde) (from
2 sources and sinks since 1880. While there is little debate that excess carbon dioxide in the industrial era has mostly come from burning fossil fuels, the future strength of land and ocean carbon sinks is an area of study. (from Attribution of recent climate change)
Quantitative analysis: Energy flows between space, the atmosphere, and Earth's surface, with greenhouse gases in the atmosphere capturing a substantial portion of the heat reflected from the earth's surface. (from Greenhouse effect)
Carbon dioxide in Earth's atmosphere)
This diagram of the fast carbon cycle shows the movement of carbon between land, atmosphere, and oceans in billions of metric tons of carbon per year. Yellow numbers are natural fluxes, red are human contributions, white are stored carbon. (from
Attribution of recent climate change)
Modeled simulation of the effect of various factors (including GHGs, Solar irradiance) singly and in combination, showing in particular that solar activity produces a small and nearly uniform warming, unlike what is observed. (from
Greenhouse gases allow sunlight to pass through the atmosphere, but then absorb and reflect the infrared radiation (heat) the planet emits (from
Attribution of recent climate change)
Observed temperature from NASA vs the 1850–1900 average used by the IPCC as a pre-industrial baseline. The primary driver for increased global temperatures in the industrial era is human activity, with natural forces adding variability. (from
Did you know –
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Plant Productivity in a Warming World
: The past decade is the warmest on record since instrumental measurements began in the 1880s. Previous research suggested that in the '80s and '90s, warmer global temperatures and higher levels of precipitation—factors associated with climate change
—were generally good for plant productivity. An updated analysis published this week in Science indicates that as temperatures have continued to rise, the benefits to plants are now overwhelmed by longer and more frequent droughts
. High-resolution data from the Moderate-Resolution Imaging Spectroradiometer
, or MODIS, indicate a net decrease in net primary production (NPP) from 2000-2009, as compared to the previous two decades. This narrated video gives an overview of NPP and the carbon cycle
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