Graeme Stephens | |
---|---|
Born | Graeme Leslie Stephens |
Alma mater | University of Melbourne (BS, PhD) [1] |
Known for | CloudSat [2] |
Awards | Jule G. Charney Award (2005) |
Scientific career | |
Fields | Atmospheric sciences |
Institutions | Caltech Colorado State University [3] University of Reading University of Melbourne |
Thesis | The transfer of radiation in cloudy atmospheres (1977) |
Website | science |
Graeme Leslie Stephens FRS [4] is director of the center for climate sciences at the NASA Jet Propulsion Laboratory at the California Institute of Technology [5] and professor of earth observation the University of Reading. [6] [7]
Stephens was educated at the University of Melbourne in Australia where he received a Bachelor of Science degree in Physics 1973 in followed by a PhD in meteorology in 1977. [1]
Stephens research has provided leadership in three major disciplinary areas of Earth sciences:
Stephens has pioneered quantitative uses of global Earth observations and combined this with theory to study Earth's climate change feedback. [4] He provided leadership in designing and developing international satellite programs exemplified by his creation and leadership of the decade long CloudSat satellite mission [2] that is providing novel insights and understanding of the Earth's clouds, precipitation and their role in climate. [4] [3] [8]
Stephens was elected a member of the National Academy of Engineering of the United States in 2015, [4] received the Jule G. Charney Award of the American Meteorological Society for pioneering advances in understanding and measuring radiation processes and their role in climate, and received the Gold Medal of the International Radiation Commission in recognition of world leading contributions to the radiation community. [4] He also received National Aeronautics Space Administration, Exceptional Public Service Medal. [4] In 2025 he received the Carl-Gustaf Rossby Research Medal of the American Meteorological Society. [9]
He was elected a Fellow of the Royal Society in 2018. [4]
Cirrus is a genus of high cloud made of ice crystals. Cirrus clouds typically appear delicate and wispy with white strands. Cirrus are usually formed when warm, dry air rises, causing water vapor deposition onto rocky or metallic dust particles at high altitudes. Globally, they form anywhere between 4,000 and 20,000 meters above sea level, with the higher elevations usually in the tropics and the lower elevations in more polar regions.
Numerical climate models are mathematical models that can simulate the interactions of important drivers of climate. These drivers are the atmosphere, oceans, land surface and ice. Scientists use climate models to study the dynamics of the climate system and to make projections of future climate and of climate change. Climate models can also be qualitative models and contain narratives, largely descriptive, of possible futures.
Cloud feedback is a type of climate change feedback, where the overall cloud frequency, height, and the relative fraction of the different types of clouds are altered due to climate change, and these changes then affect the Earth's energy balance. On their own, clouds are already an important part of the climate system, as they consist of water vapor, which acts as a greenhouse gas and so contributes to warming; at the same time, they are bright and reflective of the Sun, which causes cooling. Clouds at low altitudes have a stronger cooling effect, and those at high altitudes have a stronger warming effect. Altogether, clouds make the Earth cooler than it would have been without them.
Keith Peter Shine FRS is the Regius Professor of Meteorology and Climate Science at the University of Reading. He is the first holder of this post, which was awarded to the university by Queen Elizabeth II to mark her Diamond Jubilee.
Richard Siegmund Lindzen is an American atmospheric physicist known for his work in the dynamics of the middle atmosphere, atmospheric tides, and ozone photochemistry. He is the author of more than 200 scientific papers. From 1972 to 1982, he served as the Gordon McKay Professor of Dynamic Meteorology at Harvard University. In 1983, he was appointed as the Alfred P. Sloan Professor of Meteorology at the Massachusetts Institute of Technology, where he would remain until his retirement in 2013. Lindzen has disputed the scientific consensus on climate change and criticizes what he has called "climate alarmism".
The Carl-Gustaf Rossby Research Medal is the highest award for atmospheric science of the American Meteorological Society. It is presented to individual scientists, who receive a medal. Named in honor of meteorology and oceanography pioneer Carl-Gustaf Rossby, who was also its second (1953) recipient.
Radiative forcing is a concept used in climate science to quantify the change in energy balance in Earth's atmosphere. Various factors contribute to this change in energy balance, such as concentrations of greenhouse gases and aerosols, and changes in surface albedo and solar irradiance. In more technical terms, it is defined as "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. Radiative forcing on Earth is meaningfully evaluated at the tropopause and at the top of the stratosphere. It is quantified in units of watts per square meter, and often summarized as an average over the total surface area of the globe.
Nephology is the study of clouds and cloud formation. British meteorologist Luke Howard was a major researcher within this field, establishing a cloud classification system. While this branch of meteorology still exists today, the term nephology, or nephologist is rarely used. The term came into use at the end of the nineteenth century, and fell out of common use by the middle of the twentieth. Recently, interest in nephology has increased as some meteorologists have begun to focus on the relationship between clouds and global warming, which is a source of uncertainty regarding "estimates and interpretations of the Earth’s changing energy budget."
Earth's energy budget is the balance between the energy that Earth receives from the Sun and the energy the Earth loses back into outer space. Smaller energy sources, such as Earth's internal heat, are taken into consideration, but make a tiny contribution compared to solar energy. The energy budget also takes into account how energy moves through the climate system. The Sun heats the equatorial tropics more than the polar regions. Therefore, the amount of solar irradiance received by a certain region is unevenly distributed. As the energy seeks equilibrium across the planet, it drives interactions in Earth's climate system, i.e., Earth's water, ice, atmosphere, rocky crust, and all living things. The result is Earth's climate.
CloudSat is a Passivated NASA Earth observation satellite, which was launched on a Delta II rocket on April 28, 2006, and is awaiting disposal. It used radar to measure the altitude and properties of clouds, adding to the information on the relationship between clouds and climate to help resolve questions about global warming.
A runaway greenhouse effect will occur when a planet's atmosphere contains greenhouse gas in an amount sufficient to block thermal radiation from leaving the planet, preventing the planet from cooling and from having liquid water on its surface. A runaway version of the greenhouse effect can be defined by a limit on a planet's outgoing longwave radiation which is asymptotically reached due to higher surface temperatures evaporating water into the atmosphere, increasing its optical depth. This positive feedback means the planet cannot cool down through longwave radiation and continues to heat up until it can radiate outside of the absorption bands of the water vapour.
In climate science, longwave radiation (LWR) is electromagnetic thermal radiation emitted by Earth's surface, atmosphere, and clouds. It may also be referred to as terrestrial radiation. This radiation is in the infrared portion of the spectrum, but is distinct from the shortwave (SW) near-infrared radiation found in sunlight.
Veerabhadran "Ram" Ramanathan is Edward A. Frieman Endowed Presidential Chair in Climate Sustainability Scripps Institution of Oceanography, University of California, San Diego. He has contributed to many areas of the atmospheric and climate sciences including developments to general circulation models, atmospheric chemistry, and radiative transfer. He has been a part of major projects such as the Indian Ocean Experiment (INDOEX) and the Earth Radiation Budget Experiment (ERBE), and is known for his contributions to the areas of climate physics, Climate Change and atmospheric aerosols research. He is now the Chair of Bending the Curve: Climate Change Solutions education project of University of California. He has received numerous awards, and is a member of the US National Academy of Sciences. He has spoken about the topic of global warming, and written that "the effect of greenhouse gases on global warming is, in my opinion, the most important environmental issue facing the world today."
Robert Donald Cess was a professor of atmospheric sciences at Stony Brook University. He was born in Portland, Oregon. Cess earned his bachelor of science degree in mechanical engineering from Oregon State University and his master's degree from Purdue University in Indiana in 1956. He received a Ph.D. from the University of Pittsburgh in 1959. He is a recognized leader in the fields of climate change and atmospheric radiation transfer. His research interests involved modeling of climate feedbacks that can either amplify or diminish global climate change, and interpreting surface and satellite remote sensing data.
Isaac Meyer Held is an American meteorologist. He is a retired senior research scientist at the Geophysical Fluid Dynamics Laboratory. Held was elected to the United States National Academy of Sciences in 2003.
Julia Mary Slingo is a British meteorologist and climate scientist. She was Chief Scientist at the Met Office from 2009 until 2016. She is also a visiting professor in the Department of Meteorology at the University of Reading, where she held, prior to appointment to the Met Office, the positions of Director of Climate Research in the Natural Environment Research Council (NERC) National Centre for Atmospheric Science and founding director of the Walker Institute for Climate System Research.
The Jule G. Charney Award is the American Meteorological Society's award granted to "individuals in recognition of highly significant research or development achievement in the atmospheric or hydrologic sciences". The prize was originally known as the Second Half Century Award, and first awarded to mark to fiftieth anniversary of the society.
Amy C. Clement is an atmospheric and marine scientist studying and modeling global climate change at the University of Miami's Rosenstiel School of Marine, Atmospheric, and Earth Science.
Lin Chambers is an American physical scientist. She has developed and contributed to multiple international programs around science education and citizen science at NASA Langley Research Center.
Fixed anvil temperature hypothesis is a physical hypothesis that describes the response of cloud radiative properties to rising surface temperatures. It presumes that the temperature at which radiation is emitted by anvil clouds is constrained by radiative processes and thus does not change in response to surface warming. Since the amount of radiation emitted by clouds is a function of their temperature, it implies that it does not increase with surface warming and thus a warmer surface does not increase radiation emissions by cloud tops. The mechanism has been identified both in climate models and observations of cloud behaviour, it affects how much the world heats up for each extra tonne of greenhouse gas in the atmosphere. However, some evidence suggests that it may be more correctly formulated as decreased anvil warming rather than no anvil warming.
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