There are several kinds of physical evidence for climate change. Some of these include: Aerosols, Land-cover changes, Instrumental records, and Other archives. Some scientists also focus on the chemistry of the atmosphere, such as carbon dioxide and methane. These are all important types of physical evidence.
Instrumental records
One of the major types of physical evidence for climate change is the instrumental record. These are data from thermometers that record changes in temperature over time. The US Historical Climatology Network collects these data from weather stations across the country. For instance, it has compiled monthly mean temperature data for the US since 1849. This data reveals a significant range of variation related to the annual cycle of temperature change.
Instrumental records of temperature are the most reliable form of physical evidence for climate change. The longest instrumental temperature record is the CET dataset, which began in 1659 in Central England. This record is considered reliable for near-surface temperature change, but there is a lack of long-term data on other time scales.
Other archives
Several types of archives are available to determine past climates. In particular, paleoclimatologists collect sediment cores and tree ring patterns from various locations. These ancient archives can span thousands to millions of years. In addition, scientists can examine fossils from prehistoric eras and study sedimentary rocks. They can also analyze the structures of ocean sediments.
The observation of climate change through direct measurements, biogeochemical measurements, and remote sensing from satellites and ground stations can help scientists understand past climates. In addition, paleoclimate archives provide long-term context for past climates. Researchers can compare past climate conditions through these archives, which document the behavior of slow climate system components, such as the carbon cycle, ice sheets, and the deep ocean.
Aerosols
There are two major types of aerosols: natural and anthropogenic. These particles vary greatly in size, composition, and chemical properties and interact with the atmosphere in complicated, nonlinear ways. Aerosols are classified based on their composition, which consists of a combination of precursor gases and individual particles. They have short-lived lifetimes in the troposphere, which range from days to weeks, depending on their chemical composition and hygroscopic properties.
Besides atmospheric aerosols, there are other types of anthropogenic aerosols. These particles are injected into the atmosphere and form in the troposphere. Examples of primary aerosols include sea salt from ocean spray, desert dust, volcanic mineral emissions, and re-entrained road dust. Secondary aerosols, on the other hand, are particles produced by condensation of gases. Primary aerosol particles are usually larger than secondary aerosol particles.
Land-cover changes
Land-cover changes are among the most important physical evidence for climate change, as they influence the concentration of greenhouse gases in the atmosphere. While the link between land-cover changes and climate change is complex, it is a significant contributor to the global climate. Land-cover changes also affect mountain snowpack and vegetation cover, which can change water availability for agriculture and other processes.
In some regions, deforestation may be contributing to global warming. This is because deforestation causes temperate and boreal regions to cool. However, this effect is not directly related to the deforestation effect, as it involves non-radiative processes.
CO2 concentrations
Since the 1950s, the Mauna Loa observatory has been tracking CO2 concentrations in the atmosphere of Earth. CO2 concentrations during ice ages were around 180 parts per million, but by the early twentieth century they had risen to about 280 ppm. In other words, human activity has more than doubled the concentration of CO2 in the atmosphere. However, the reasons for this warming are still not fully understood.
The total CO2 concentration in the atmosphere is highly correlated with the total amount of CO2 emitted by fossil fuels. This tight correlation is referred to as the human fingerprint of climate change. The increased CO2 concentrations in the atmosphere has caused a complex set of changes in the planet.
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