Systematic observation of the climate system is carried out by national meteorological agencies under the coordination of UN’s World Meteorological Organization (WMO). These national agencies take measurements at standard preset times and places, monitoring the atmosphere, ocean, and terrestrial systems. Since national monitoring systems all form part of a global network, it is vital that there is as much consistency as possible in the way observations are made across national boundaries and over time. This includes accuracy, the variables measured, and the units they are measured in.
Monitoring starts with weather observations from ground-based, balloon-borne, radars, and marine-buoy sensors—over ten thousand land and ocean observation locations worldwide in all. Countries around the world all share their observations to provide a continuous data collection of global weather. These weather observations are then aggregated to form climate information.
Many institutions around the world collaborate in collecting and analyzing climate data. These groups include the National Centers for Environmental Information (US), Geophysical Fluid Dynamics Lab (US), Goddard Institute for Space Studies (US), National Center for Atmospheric Research (US), the Hadley Center for Climate Prediction and Research (UK), and the Max Planck Institute for Meteorology (Germany), just to name a few. Research results from these groups are often published in peer-review journals. Every few years, the Intergovernmental Panel on Climate Change (IPCC), a UN-sponsored group that is made up of scientists from universities and research institutions, summarizes results from these journals in assessment reports.
There are two types of weather satellites. A geostationary satellite is in an orbit (at about 36000 Km above the earth’s equator) that has an orbital period equal to the earth’s rotational period of one day, so it can observe the same area on earth continuously. For example, the US GOES East (a geostationary satellite) can continuously observe the weather over the eastern half of the US and the Atlantic Ocean, while GOES West does the same for the Pacific Ocean and the western half of US. Europe, Japan, China, and India all have their own geostationary and polar orbiting weather satellites. Solar-synchronous polar orbiter (at about 800 Km above the earth) is the other type of weather satellite, which observes the same area twice a day, in the same hour every day, once in the daytime and once at night. These two types of satellites are complementary in providing weather observation. Because of a polar orbiter’s low orbit, it can provide detailed information about the weather twice per day, while geostationary satellite provides continuous observations, but with less details.
In the U.S., NASA, NOAA, and USGS conduct climate monitoring using satellites. In particular, US conducts a long-term program, called the Decadal Survey, in climate monitoring using satellites. A sample of these satellites include:
* Orbiting Carbon Observatory monitors CO2 distribution in the atmosphere
* GRACE Mission monitors global ice mass-change
* ICESAT-2 satellite monitors changes in height in glaciers and forests
* Terra and Aqua satellites monitors changes in the atmosphere, land, and ocean
* The Landsat series monitors land use and land cover changes in the climate time scale
A sample of European Space Agency (ESA) satellites that conduct climate monitoring include:
* SENTINEL-1, composed of two satellites, performs radar imaging for land change monitoring
* SENTINEL-2 uses optical sensors to monitor land changes
* SENTINEL-3, composed of three satellites, monitors sea-surface topography, sea and land surface temperature, ocean and land color