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.
Extreme weather includes unexpected, unusual, severe, or unseasonal weather; weather at the extremes of the historical distribution—the range that has been seen in the past. Extreme events are based on a location's recorded weather history. They are defined as lying in the most unusual ten percent. The main types of extreme weather include heat waves, cold waves and heavy precipitation or storm events, such as tropical cyclones. The effects of extreme weather events are economic costs, loss of human lives, droughts, floods, landslides. Severe weather is a particular type of extreme weather which poses risks to life and property.
There is a nearly unanimous scientific consensus that the Earth has been consistently warming since the start of the Industrial Revolution, that the rate of recent warming is largely unprecedented, and that this warming is mainly the result of a rapid increase in atmospheric carbon dioxide (CO2) caused by human activities. The human activities causing this warming include fossil fuel combustion, cement production, and land use changes such as deforestation, with a significant supporting role from the other greenhouse gases such as methane and nitrous oxide. This human role in climate change is considered "unequivocal" and "incontrovertible".
Kevin Edward Trenberth worked as a climate scientist in the Climate Analysis Section at the US National Center for Atmospheric Research (NCAR). He was a lead author of the 1995, 2001 and 2007 IPCC assessment reports. He also played major roles in the World Climate Research Programme (WCRP), for example in its Tropical Oceans Global Atmosphere program (TOGA), the Climate Variability and Predictability (CLIVAR) program, and the Global Energy and Water Exchanges (GEWEX) project.
Climate commitment describes the fact that Earth's climate reacts with a delay to influencing factors such as the growth and the greater presence of greenhouse gases. Climate commitment studies attempt to assess the amount of future global warming that is "committed" under the assumption of some constant or some evolving level of forcing. The constant level often used for illustrative purposes is that due to CO2 doubling or quadrupling relative to the pre-industrial level; or the present level of forcing.
Polar amplification is the phenomenon that any change in the net radiation balance tends to produce a larger change in temperature near the poles than in the planetary average. This is commonly referred to as the ratio of polar warming to tropical warming. On a planet with an atmosphere that can restrict emission of longwave radiation to space, surface temperatures will be warmer than a simple planetary equilibrium temperature calculation would predict. Where the atmosphere or an extensive ocean is able to transport heat polewards, the poles will be warmer and equatorial regions cooler than their local net radiation balances would predict. The poles will experience the most cooling when the global-mean temperature is lower relative to a reference climate; alternatively, the poles will experience the greatest warming when the global-mean temperature is higher.
Warren Morton Washington was an American atmospheric scientist, a chair of the National Science Board, and a Distinguished Scholar at the National Center for Atmospheric Research (NCAR) in Boulder, Colorado. His research was part of the United Nations Intergovernmental Panel on Climate Change that shared the 2007 Nobel Peace Prize with Al Gore. In 2019, he was awarded the Tyler Prize for Environmental Achievement.
Sea ice in the Arctic region has declined in recent decades in area and volume due to climate change. It has been melting more in summer than it refreezes in winter. Global warming, caused by greenhouse gas forcing is responsible for the decline in Arctic sea ice. The decline of sea ice in the Arctic has been accelerating during the early twenty-first century, with a decline rate of 4.7% per decade. Summertime sea ice will likely cease to exist sometime during the 21st century.
Gerald Allen "Jerry" Meehl is a climate scientist who has been a senior scientist at the National Center for Atmospheric Research since 2001.
Julie Michelle Arblaster is an Australian scientist. She is a Professor in the School of Earth, Atmosphere and Environment at Monash University. She was a contributing author on reports for which the Intergovernmental Panel on Climate Change (IPCC) was a co-recipient of the 2007 Nobel Peace Prize. Arblaster was a lead author on Chapter 12 of the IPCC Working Group I contribution to the IPCC Fifth Assessment Report in 2013. She has received the 2014 Anton Hales Medal for research in earth sciences from the Australian Academy of Science, and the 2017 Priestley Medal from the Australian Meteorological and Oceanographic Society. She has been ranked as one of the Top Influential Earth Scientists of 2010-2020, based on citations and discussion of her work.
Sonia Isabelle Seneviratne is a Swiss climate scientist, professor at the Institute for Atmospheric and Climate Science of the ETH Zurich. She is a specialist of extreme climate events.
Cecilia M. Bitz is an American climatologist known for her research on sea ice and high-latitude climate change. She is a professor and chair in the Atmospheric Sciences Department, as well as the director of the Program on Climate Change at the University of Washington. She was featured on NPR's All Things Considered segment to speak about factors that lead to sea ice loss in 2007, and testified before the United States Senate committee of Energy and Natural Resources on arctic opportunities in 2015.
Maura E. Hagan is a Professor Emeritus of Physics and a former Dean of the College of Science at Utah State University. She is a Fellow of both the American Meteorological Society and the American Geophysical Union, and was elected a member of the National Academy of Sciences in 2019.
The skin temperature of an atmosphere is the temperature of a hypothetical thin layer high in the atmosphere that is transparent to incident solar radiation and partially absorbing of infrared radiation from the planet. It provides an approximation for the temperature of the tropopause on terrestrial planets with greenhouse gases present in their atmospheres.
Natalya Gomez is a professor, researcher, cryosphere and sea level expert whose research primarily centers around the interactions between ice sheets, sea level, and earth in the past, present and future. Gomez is a professor at McGill University, a Canada Research Chair in Geodynamics of Ice sheet - Sea level interactions, and received the AGU Cryosphere Early Career Award in 2019.
Caroline C. Ummenhofer is a physical oceanographer at the Woods Hole Oceanographic Institution where she studies extreme weather events with a particular focus on the Indian Ocean. Ummenhofer makes an effort to connect her discoveries about predicting extreme weather events and precipitation to helping the nations affected.
Emily V. Fischer is an atmospheric chemist and an associate professor in the department of atmospheric science at Colorado State University. She earned notoriety from her work on the WE-CAN project and on PAN, specifically its role in changing the distribution of oxidants in the troposphere. She has received many honors including the prestigious James B. Macelwane Medal which is "given annually to three to five early career scientists in recognition of their significant contributions to Earth and space science." Fischer is also a role model and activist in galvanizing support for women in STEM fields.
A marine heatwave is a period of abnormally high sea surface temperatures compared to the typical temperatures in the past for a particular season and region. Marine heatwaves are caused by a variety of drivers. These include shorter term weather events such as fronts, intraseasonal events, annual, and decadal (10-year) modes like El Niño events, and human-caused climate change. Marine heatwaves affect ecosystems in the oceans. For example, marine heatwaves can lead to severe biodiversity changes such as coral bleaching, sea star wasting disease, harmful algal blooms, and mass mortality of benthic communities. Unlike heatwaves on land, marine heatwaves can extend over vast areas, persist for weeks to months or even years, and occur at subsurface levels.
Natalie Mahowald is an American Earth scientist who is the Irving Porter Church Professor of Engineering at Cornell University. Her research considers atmospheric transport of biogeochemically-relevant species, and the impact of humans on their environments.
Bette Otto-Bliesner is an earth scientist known for her modeling of Earth's past climate and its changes over different geological eras.
