The global temperature record shows the fluctuations of the temperature of the atmosphere and the oceans through various spans of time. The most detailed information exists since 1850, when methodical thermometer-based records began. There are numerous estimates of temperatures since the end of the Pleistocene glaciation, particularly during the current Holocene epoch. Older time periods are studied by paleoclimatology.
Weather balloon radiosonde measurements of atmospheric temperature at various altitudes begin to show an approximation of global coverage in the 1950s. Since December 1978, microwave sounding units on satellites have produced data which can be used to infer temperatures in the troposphere.
Several groups have analyzed the satellite data to calculate temperature trends in the troposphere. Both the University of Alabama in Huntsville (UAH) and the private, NASA funded, corporation Remote Sensing Systems RSS (RSS) find an upward trend.
In 2004 Fu et al. found trends of +0.19 degrees Celsius per decade when applied to the RSS dataset. Vinnikov and Grody found 0.20 degrees Celsius per decade up between 1978 and 2005, since which the dataset has not been updated.
Detailed information exists since 1850, when methodical thermometer-based records began.
Proxy measurements can be used to reconstruct the temperature record before the historical period. Quantities such as tree ring widths, coral growth, isotope variations in ice cores, ocean and lake sediments, cave deposits, fossils, ice cores, borehole temperatures, and glacier length records are correlated with climatic fluctuations. From these, proxy temperature reconstructions of the last 2000 years have been performed for the northern hemisphere, and over shorter time scales for the southern hemisphere and tropics.
Geographic coverage by these proxies is necessarily sparse, and various proxies are more sensitive to faster fluctuations. For example, tree rings, ice cores, and corals generally show variation on an annual time scale, but borehole reconstructions rely on rates of thermal diffusion, and small scale fluctuations are washed out. Even the best proxy records contain far fewer observations than the worst periods of the observational record, and the spatial and temporal resolution of the resulting reconstructions is correspondingly coarse. Connecting the measured proxies to the variable of interest, such as temperature or rainfall, is highly non-trivial. Data sets from multiple complementary proxies covering overlapping time periods and areas are reconciled to produce the final reconstructions.
Proxy reconstructions extending back 2,000 years have been performed, but reconstructions for the last 1,000 years are supported by more and higher quality independent data sets. These reconstructions indicate:
As well as natural, numerical proxies (tree-ring widths, for example) there exist records from the human historical period that can be used to infer climate variations, including: reports of frost fairs on the Thames; records of good and bad harvests; dates of spring blossom or lambing; extraordinary falls of rain and snow; and unusual floods or droughts. Such records can be used to infer historical temperatures, but generally in a more qualitative manner than natural proxies.
Recent evidence suggests that a sudden and short-lived climatic shift between 2200 and 2100 BCE occurred in the region between Tibet and Iceland, with some evidence suggesting a global change. The result was a cooling and reduction in precipitation. This is believed to be a primary cause of the collapse of the Old Kingdom of Egypt.
Many estimates of past temperatures have been made over Earth's history. The field of paleoclimatology includes ancient temperature records. As the present article is oriented toward recent temperatures, there is a focus here on events since the retreat of the Pleistocene glaciers. The 10,000 years of the Holocene epoch covers most of this period, since the end of the Northern Hemisphere's Younger Dryas millennium-long cooling. The Holocene Climatic Optimum was generally warmer than the 20th century, but numerous regional variations have been noted since the start of the Younger Dryas.
Even longer term records exist for few sites: the recent Antarctic EPICA core reaches 800 kyr; many others reach more than 100,000 years. The EPICA core covers eight glacial/interglacial cycles. The NGRIP core from Greenland stretches back more than 100 kyr, with 5 kyr in the Eemian interglacial. Whilst the large-scale signals from the cores are clear, there are problems interpreting the detail, and connecting the isotopic variation to the temperature signal.
On longer time scales, sediment cores show that the cycles of glacials and interglacials are part of a deepening phase within a prolonged ice age that began with the glaciation of Antarctica approximately 40 million years ago. This deepening phase, and the accompanying cycles, largely began approximately 3 million years ago with the growth of continental ice sheets in the Northern Hemisphere. Gradual changes in Earth's climate of this kind have been frequent during the Earth's 4500 million year existence and most often are attributed to changes in the configuration of continents and ocean sea ways.
A number of significant scientific events occurred in 2013, including the discovery of numerous Earthlike exoplanets, the development of viable lab-grown ears, teeth, livers and blood vessels, and the atmospheric entry of the most destructive meteor since 1908. The year also saw successful new treatments for diseases such as HIV, Usher syndrome and leukodystrophy, and a major expansion in the use and capabilities of technologies such as 3D printing and autonomous cars.
The United Nations designated 2013 the International Year of Water Cooperation.2016 in science
A number of significant scientific events occurred in 2016. The United Nations declared 2016 the International Year of Pulses.Carbon dioxide in Earth's atmosphere
Carbon dioxide (CO2) is an important trace gas in Earth's atmosphere. It is an integral part of the carbon cycle, a biogeochemical cycle in which carbon is exchanged between the Earth's oceans, soil, rocks and the biosphere. Plants and other photoautotrophs use solar energy to produce carbohydrate from atmospheric carbon dioxide and water by photosynthesis. Almost all other organisms depend on carbohydrate derived from photosynthesis as their primary source of energy and carbon compounds. CO2 absorbs and emits infrared radiation at wavelengths of 4.26 µm (asymmetric stretching vibrational mode) and 14.99 µm (bending vibrational mode) and consequently is a greenhouse gas that plays a significant role in influencing Earth's surface temperature through the greenhouse effect.Concentrations of CO2 in the atmosphere were as high as 4,000 parts per million (ppm) during the Cambrian period about 500 million years ago to as low as 180 ppm during the Quaternary glaciation of the last two million years. Estimates based on reconstructed temperature records suggests that the amount of CO2 during the last 420 million years ago was with ~2000 ppm highest during the Devonian (∼400 Myrs ago) and Triassic (220–200 Myrs ago), with a few maximum estimates ranging up to ∼3,700±1,600 ppm (215 Myrs ago). Global annual mean CO2 concentration has increased by more than 45% since the start of the Industrial Revolution, from 280 ppm during the 10,000 years up to the mid-18th century to 410 ppm as of mid-2018. The present concentration is the highest in the last 800,000 and possibly even the last 20 million years. The increase has been caused by human activities, particularly the burning of fossil fuels and deforestation. This increase of CO2 and other long-lived greenhouse gases in Earth's atmosphere has produced the current episode of global warming. About 30–40% of the CO2 released by humans into the atmosphere dissolves into oceans, rivers and lakes, which has produced ocean acidification.Glossary of climate change
This article serves as a glossary of climate change terms. It lists terms that are related to global warming.HadCRUT
HadCRUT is the dataset of monthly instrumental temperature records formed by combining the sea surface temperature records compiled by the Hadley Centre of the UK Met Office and the land surface air temperature records compiled by the Climatic Research Unit (CRU) of the University of East Anglia.The data is provided on a grid of boxes covering the globe, with values provided for only those boxes containing temperature observations in a particular month and year. Interpolation is not applied to infill missing values. The first version of HadCRUT initially spanned the period 1881–1993, and this was later extended to begin in 1850 and to be regularly updated to the current year/month in near real-time.Instrumental temperature record
The instrumental temperature record provides the temperature of Earth's climate system from the historical network of in situ measurements of surface air temperatures and ocean surface temperatures. Data are collected at thousands of meteorological stations, buoys and ships around the globe. The longest-running temperature record is the Central England temperature data series, which starts in 1659. The longest-running quasi-global record starts in 1850. In recent decades more extensive sampling of ocean temperatures at various depths have begun allowing estimates of ocean heat content but these do not form part of the global surface temperature datasets.Robert Rohde
Robert Andrew Rohde is an American physicist and former graduate student at the University of California, Berkeley, where he studied under Richard A. Muller. He received his PhD in 2010 with a thesis entitled "The Development and Use of the Berkeley Fluorescence Spectrometer to Characterize Microbial Content and Detect Volcanic Ash in Glacial Ice." He is also the founder of the website Global Warming Art and a Wikipedia editor under the username "Dragons Flight".