![]() Observations show increasing surface air and ocean temperatures over most regions and diminishing snow and ice cover at high latitudes. Projected warming over the next century will likely place global temperatures in a range not seen in millions of years of geologic history.Įarth’s climate is warming. Global temperatures were last on par with the present ones in the previous Interglacial Period (125,000 years ago), when sea level was 6–9 m (20–30 ft) higher than today. Proxies, which are indirect measurements of past temperature obtained from archives, such as tree rings, corals, ice cores, lake and marine sediments, and cave stalagmites, reveal that the rate and magnitude of the current global temperature change is likely exceptional in the context of the last two thousand years. The IPCC (2013), USGCRP (2017), and USGCRP (2018) indicate that it is extremely likely that human influence has been the dominant cause of the observed warming since the mid-twentieth century. These natural fluctuations have neither the magnitude nor the spatial characteristics to explain the observed warming of Earth’s average surface temperature over the past several decades. The influence of these relatively short-period fluctuations is factored into climate change analyses. ![]() The observed warming rate varies from place to place and from decade to decade because of natural climate variations, such as natural swings between El Niño and La Niña on time scales of two to seven years, and variations in ocean circulation in the Pacific and Atlantic basins on decadal to multi-decadal timescales. The increase in global average surface temperature over the past half-century cannot be fully explained by natural climate variability, e.g., responses to Earth’s orbital changes over thousands of years, or natural climate forcing such as from solar or volcanic variability. The latitudinal and seasonal observations of the surface warming and the observed warming of the troposphere and cooling of the stratosphere are consistent with theoretical expectations from increased concentrations of greenhouse gases. Its manifestation includes the warming of the atmosphere and oceans, intensification of the heaviest precipitation over continental areas, increasing upper-ocean acidity, increasing frequency and intensity of daily temperature extremes, reductions in Northern Hemisphere snow and ice, and rising global sea level. Research has found a human influence on the climate of the past several decades. ![]() A particular focus is on climate change in recent decades and its connection to human-produced greenhouse gases. It is based on peer-reviewed scientific literature and reflects current scientific understanding. ![]() This statement provides an overview of how and why global climate has changed over the past century and why it will continue to change in the future. The AMS Information Statement seeks to provide a trustworthy, objective, and scientifically up-to-date explanation of climate change to the public using easily understood language. 2007 Climate Change Statement An Information Statement of the American Meteorological Society (Adopted by the AMS Council on 15 April 2019)
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