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The scientific community has been investigating the causes of climate change for decades. After thousands of studies, it came to a consensus, where it is "unequivocal that human influence has warmed the atmosphere, ocean and land since pre-industrial times." This consensus is supported by around 200 scientific organizations worldwide, The dominant role in this climate change has been played by the direct emissions of carbon dioxide from the burning of fossil fuels. Indirect CO2 emissions from land use change, and the emissions of methane, nitrous oxide and other greenhouse gases play major supporting roles.
Satellite temperature measurements are inferences of the temperature of the atmosphere at various altitudes as well as sea and land surface temperatures obtained from radiometric measurements by satellites. These measurements can be used to locate weather fronts, monitor the El Niño-Southern Oscillation, determine the strength of tropical cyclones, study urban heat islands and monitor the global climate. Wildfires, volcanos, and industrial hot spots can also be found via thermal imaging from weather satellites.
The instrumental temperature record is a record of temperatures within Earth's climate based on direct measurement of air temperature and ocean temperature, using thermometers and other thermometry devices. Instrumental temperature records are distinguished from indirect reconstructions using climate proxy data such as from tree rings and ocean sediments. Instrument-based data are collected from thousands of meteorological stations, buoys and ships around the globe. Whilst many heavily-populated areas have a high density of measurements, observations are more widely spread in sparsely populated areas such as polar regions and deserts, as well as over many parts of Africa and South America. Measurements were historically made using mercury or alcohol thermometers which were read manually, but are increasingly made using electronic sensors which transmit data automatically. Records of global average surface temperature are usually presented as anomalies rather than as absolute temperatures. A temperature anomaly is measured against a reference value. For example, a commonly used baseline period is the time period 1951-1980.
Global cooling was a conjecture, especially during the 1970s, of imminent cooling of the Earth culminating in a period of extensive glaciation, due to the cooling effects of aerosols or orbital forcing. Some press reports in the 1970s speculated about continued cooling; these did not accurately reflect the scientific literature of the time, which was generally more concerned with warming from an enhanced greenhouse effect.
Global dimming is a decline in the amount of sunlight reaching the Earth's surface, a measure also known as global direct solar irradiance. It was observed soon after the first systematic measurements of solar irradiance began in the 1950s, and continued until 1980s, with an observed reduction of 4–5% per decade, even though solar activity did not vary more than the usual at the time. Instead, global dimming had been attributed to an increase in atmospheric particulate matter, predominantly sulfate aerosols, as the result of rapidly growing air pollution due to post-war industrialization. After 1980s, reductions in particulate emissions have also caused a "partial" reversal of the dimming trend, which has sometimes been described as a global brightening. This reversal is not yet complete, and it has also been globally uneven, as some of the brightening over the developed countries in the 1980s and 1990s had been counteracted by the increased dimming from the industrialization of the developing countries and the expansion of the global shipping industry, although they have also been making rapid progress in cleaning up air pollution in the recent years.
Roy Warren Spencer is an American meteorologist. He is a principal research scientist at the University of Alabama in Huntsville, and the U.S. Science Team leader for the Advanced Microwave Scanning Radiometer (AMSR-E) on NASA's Aqua satellite. He has served as senior scientist for climate studies at NASA's Marshall Space Flight Center. He is known for his satellite-based temperature monitoring work, for which he was awarded the American Meteorological Society's Special Award. Spencer disagrees with the scientific consensus that most global warming in the past 50 years is the result of human activity, instead believing that anthropogenic greenhouse gas emissions have caused some warming, but that influence is small compared to natural variations in global average cloud cover.
Radiative forcing is a concept used in climate science to quantify the change in energy balance in the Earth's atmosphere caused by various factors, such as concentrations of greenhouse gases, aerosols, and changes in solar radiation. In more technical terms, it is "the change in the net, downward minus upward, radiative flux due to a change in an external driver of climate change." These external drivers are distinguished from feedbacks and variability that are internal to the climate system, and that further influence the direction and magnitude of imbalance.
The global temperature record shows the fluctuations of the temperature of the atmosphere and the oceans through various spans of time. There are numerous estimates of temperatures since the end of the Pleistocene glaciation, particularly during the current Holocene epoch. Some temperature information is available through geologic evidence, going back millions of years. More recently, information from ice cores covers the period from 800,000 years before the present time until now. A study of the paleoclimate covers the time period from 12,000 years ago to the present. Tree rings and measurements from ice cores can give evidence about the global temperature from 1,000-2,000 years before the present until now. The most detailed information exists since 1850, when methodical thermometer-based records began. Modifications on the Stevenson-type screen were made for uniform instrument measurements around 1880.
Greenhouse gases are the gases in the atmosphere that raise the surface temperature of planets such as the Earth. What distinguishes them from other gases is that they absorb the wavelengths of radiation that a planet emits, resulting in the greenhouse effect. The Earth is warmed by sunlight, causing its surface to radiate heat, which is then mostly absorbed by greenhouse gases. Without greenhouse gases in the atmosphere, the average temperature of Earth's surface would be about −18 °C (0 °F), rather than the present average of 15 °C (59 °F).
The history of the scientific discovery of climate change began in the early 19th century when ice ages and other natural changes in paleoclimate were first suspected and the natural greenhouse effect was first identified. In the late 19th century, scientists first argued that human emissions of greenhouse gases could change Earth's energy balance and climate. The existence of the greenhouse effect, while not named as such, was proposed as early as 1824 by Joseph Fourier. The argument and the evidence were further strengthened by Claude Pouillet in 1827 and 1838. In 1856 Eunice Newton Foote demonstrated that the warming effect of the sun is greater for air with water vapour than for dry air, and the effect is even greater with carbon dioxide.
Remote Sensing Systems (RSS) is a private research company founded in 1974 by Frank Wentz. It processes microwave data from a variety of NASA satellites. Most of their research is supported by the Earth Science Enterprise program. The company is based in Santa Rosa, California.
Carl Mears is a Senior Scientist, at Remote Sensing Systems, since 1998. He has worked on validation of SSM/I derived winds, and rain-flagging algorithm for the QuikScat scatterometer. He is best known for his work with Frank Wentz in developing a satellite temperature record from MSU and AMSU. Intercomparison of this record with the earlier UAH satellite temperature record, developed by John Christy and Roy Spencer, revealed deficiencies in the earlier work; specifically, the warming trend in the RSS version is larger than the UAH one.
Frank Wentz is the CEO and director of Remote Sensing Systems, a company he founded in 1974, which specializes in satellite microwave remote sensing research. Together with Carl Mears, he is best known for developing a satellite temperature record from MSU and AMSU. Intercomparison of this record with the earlier UAH satellite temperature record, developed by John Christy and Roy Spencer, revealed deficiencies in the earlier work; specifically, the warming trend in the RSS version is larger than the University of Alabama in Huntsville (UAH) one. From 1978 to 1982, Wentz was a member of NASA's SeaSat Experiment Team involved in the development of physically based retrieval methods for microwave scatterometers and radiometers. He has also investigated the effect of climate change on satellite-derived evaporation, precipitation and surface wind values. His findings are different from most climate change model predictions.
Microwave Sounding Unit temperature measurements refers to temperature measurement using the Microwave Sounding Unit instrument and is one of several methods of measuring Earth atmospheric temperature from satellites. Microwave measurements have been obtained from the troposphere since 1979, when they were included within NOAA weather satellites, starting with TIROS-N. By comparison, the usable balloon (radiosonde) record begins in 1958 but has less geographic coverage and is less uniform.
The UAH satellite temperature dataset, developed at the University of Alabama in Huntsville, infers the temperature of various atmospheric layers from satellite measurements of the oxygen radiance in the microwave band, using Microwave Sounding Unit temperature measurements.
A global warming hiatus, also sometimes referred to as a global warming pause or a global warming slowdown, is a period of relatively little change in globally averaged surface temperatures. In the current episode of global warming many such 15-year periods appear in the surface temperature record, along with robust evidence of the long-term warming trend. Such a "hiatus" is shorter than the 30-year periods that climate is classically averaged over.
Patterns of solar irradiance and solar variation have been a main driver of climate change over the millions to billions of years of the geologic time scale.
Jennifer Logan is an atmospheric scientist known for her research on how human activities influence the atmosphere, particularly with respect to biomass burning and the ozone hole.
Joyce Penner is an atmospheric scientist known for her research on climate change, especially on the impact of aerosols and clouds.
References
- 1 2 3 4 5 "Dr. John Christy Biography". University of Alabama in Huntsville. Retrieved November 14, 2019. See also archived version (archivedate=16 July 2012).
- ↑ John Christy website at UAH.
- ↑ An investigation of the general circulation associated with extreme anomalies in hemispheric mean atmospheric mass. University of Illinois. 1987. OCLC 18286111.
- ↑ "List of AMS Fellows". American Meteorological Society . Retrieved October 8, 2008.
- 1 2 Tom M. L. Wigley; et al. (April 2006). "Temperature Trends in the Lower Atmosphere – Executive Summary" (PDF). U.S. Climate Change Science Program. Archived from the original (PDF) on 2007-04-23.
- ↑ Roy Spencer; John Christy; Phillip Gentry (May 5, 2004). "New Climate Study Finds 'Global Warming' by Subtracting Cooling That Wasn't There". University of Alabama in Huntsville.
- ↑ "Appendix III – Contributors to the IPCC WGI Third Assessment Report". IPCC. 2001. Retrieved April 4, 2007.
- 1 2 David, Perlman (December 18, 2003). "Earth warming at faster pace, say top science group's leaders". San Francisco Chronicle. Retrieved April 4, 2007.
- ↑ John R. Christy; William B. Norris (February 2006). "Methodology and Results of Calculating Central California Surface Temperature Trends: Evidence of Human-Induced Climate Change?". Journal of Climate. 19 (4): 548–563. Bibcode:2006JCli...19..548C. doi:10.1175/JCLI3627.1.
- ↑ Jon Birger (May 14, 2009). "What if global-warming fears are overblown?". Fortune Magazine.
- ↑ John Christy (November 1, 2007). "My Nobel moment". Wsj.com . Dow Jones & Company.
- ↑ John Christy (November 25, 2009), House Ways and Means Committee – Written Testimony (PDF), U.S. House Ways and Means Committee, archived from the original (PDF) on July 10, 2010
- ↑ Christy & McNider (19 February 2014). "McNider and Christy: Why Kerry Is Flat Wrong on Climate Change". Wall Street Journal. Retrieved 6 April 2014.
- 1 2 "John R. Christy: Short biography". NASA. Archived from the original on March 7, 2007. Retrieved April 4, 2007.
