Albedo is the measure of the diffuse reflection of solar radiation out of the total solar radiation and measured on a scale from 0, corresponding to a black body that absorbs all incident radiation, to 1, corresponding to a body that reflects all incident radiation.
Attribution of recent climate change is the effort to scientifically ascertain mechanisms responsible for recent global warming and related climate changes on Earth. The effort has focused on changes observed during the period of instrumental temperature record, particularly in the last 50 years. This is the period when human activity has grown fastest and observations of the atmosphere above the surface have become available. According to the Intergovernmental Panel on Climate Change (IPCC), it is "extremely likely" that human influence was the dominant cause of global warming between 1951 and 2010. Likely human contribution is 93%–123% of the observed 1951–2010 temperature change.
Siegfried Fred Singer was an Austrian-born American physicist and emeritus professor of environmental science at the University of Virginia, trained as an atmospheric physicist. He was known for rejecting the scientific consensus on several issues:
The greenhouse effect is the process by which radiation from a planet's atmosphere warms the planet's surface to a temperature above what it would be without this atmosphere.
The global warming controversy concerns the public debate over whether global warming is occurring, how much has occurred in modern times, what has caused it, what its effects will be, whether any action can or should be taken to curb it, and if so what that action should be. In the scientific literature, there is a strong consensus that global surface temperatures have increased in recent decades and that the trend is caused by human-induced emissions of greenhouse gases. No scientific body of national or international standing disagrees with this view, though a few organizations with members in extractive industries hold non-committal positions, and some have attempted to convince the public that climate change is not happening, or if the climate is changing it is not because of human influence, attempting to sow doubt in the scientific consensus.
Numerical climate models use quantitative methods to simulate the interactions of the important drivers of climate, including atmosphere, oceans, land surface and ice. They are used for a variety of purposes from study of the dynamics of the climate system to projections of future climate. Climate models may also be qualitative models and also narratives, largely descriptive, of possible futures.
Global dimming is the reduction in the amount of global direct irradiance at the Earth's surface that has been observed since systematic measurements began in the 1950s. The effect varies by location, but worldwide it has been estimated to be of the order of a 4–20% reduction. However, after discounting an anomaly caused by the eruption of Mount Pinatubo in 1991, a very slight reversal in the overall trend has been observed.
Radiative forcing is the difference between solar irradiance (sunlight) absorbed by the Earth and energy radiated back to space. It is the scientific basis for the greenhouse effect on planets, and plays an important role in computational models of Earth's energy balance and climate. Changes to Earth's radiative equilibrium that cause temperatures to rise or fall over decadal periods are called climate forcings.
Climate engineering or climate intervention, commonly referred to as geoengineering, is the deliberate and large-scale intervention in the Earth's climate system. The most prominent subcategories of climate engineering are solar radiation management and carbon dioxide removal. Solar radiation management refers to offsetting the warming effect of greenhouse gases by reflecting more solar radiation (sunlight) back into space. Carbon dioxide removal refers to removing carbon dioxide gas from the atmosphere and sequestering it for long periods of time.
The faint young Sun paradox or faint young Sun problem describes the apparent contradiction between observations of liquid water early in Earth's history and the astrophysical expectation that the Sun's output would be only 70 percent as intense during that epoch as it is during the modern epoch. The paradox is this: With the young sun's output at only 70 percent of its current output, the early earth would be expected to be completely frozen but the early earth seems to have had liquid water.
The US National Center for Atmospheric Research is a US federally funded research and development center (FFRDC) managed by the nonprofit University Corporation for Atmospheric Research (UCAR) and funded by the National Science Foundation (NSF). NCAR has multiple facilities, including the I. M. Pei-designed Mesa Laboratory headquarters in Boulder, Colorado. Studies include meteorology, climate science, atmospheric chemistry, solar-terrestrial interactions, environmental and societal impacts.
Climate change includes both global warming driven by human emissions of greenhouse gases and the resulting large-scale shifts in weather patterns. Though there have been previous periods of climatic change, since the mid-20th century humans have had an unprecedented impact on Earth's climate system and caused change on a global scale.
Habibullo Ismailovich Abdussamatov is a Russian astrophysicist of Uzbek descent. He is the supervisor of the Astrometria project of the Russian section of the International Space Station and the head of Space research laboratory at the Saint Petersburg-based Pulkovo Observatory of the Russian Academy of Sciences. He believes that global warming is primarily caused by natural processes.
Henrik Svensmark is a physicist and professor in the Division of Solar System Physics at the Danish National Space Institute in Copenhagen. He is known for his theory on the effects of cosmic rays on cloud formation as an indirect cause of global warming.
Eigil Friis-Christensen was a Danish geophysicist specializing in space physics.
Solar radiation management (SRM), or solar geoengineering, is a type of climate engineering in which sunlight is reflected back to space to reduce impacts from global warming. The most discussed methods are stratospheric sulfate aerosol injection and marine cloud brightening. Localised protective or restorative methods have also been proposed regarding the protection of natural heat reflectors including sea ice, snow, and glaciers. SRM can theoretically be deployed and become fully active within months and potentially has a low financial cost. There are many physical risks and uncertainties associated with solar geoengineering including termination shock, ozone loss, and ecosystem impacts. Geopolitical risks also arise as any deployment will affect the whole planet.
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 the climate. Many other theories of climate change were advanced, involving forces from volcanism to solar variation. In the 1960s, the evidence for the warming effect of carbon dioxide gas became increasingly convincing. Some scientists also pointed out that human activities that generated atmospheric aerosols could have cooling effects as well.
Patterns of solar irradiance and solar variation has been a main driver of climate change over the millennia to gigayears of the geologic time scale, but its role in the recent warming has been found to be insignificant.
Gretchen Keppel-Aleks is an American scientist and assistant professor at the University of Michigan in the College of Engineering's department of Climate and Space Sciences and Engineering. She primarily focuses on Earth's climate and the effects of greenhouse gasses on Earth's atmosphere.
He has two children.
