You have surely heard messages from the United Nations warning the world of the danger of global warming. But do you know how the medicine behind these alerts is manufactured?
In total, scientists use seven indicators to monitor the development and state of the global climate system. These indicators constitute essential information to describe climate change.
The methods applied in this process range from observations at the seafloor to the top of the atmosphere.
Communities in Malemene, north-eastern Kenya, are facing drought conditions
1 – Average air temperature at the surface
The first important indicator is the average surface air temperature. To generate this information, air temperature about two meters above land and sea surface is combined, using information from measuring stations around the world and climate reanalysis models.
Based on six sets of global temperature data, the World Meteorological Organization calculates the annual anomaly and classification. 2023 will be the hottest year on record. Measurements began in 1850.
Moreover, the past nine years, from 2015 to 2023, were the hottest.
2- The heat content of the ocean
The second indicator is Ocean heat content. This measurement is carried out at different depths, up to two thousand metres. All databases indicate that the rate of ocean warming has increased sharply in the last two decades at all depths.
The ocean absorbed and retained about 90% of the excess heat due to increased human-caused global warming. The latest available aggregate information, pointing to 2022, reveals that ocean heat content reached a new record high this year.
Remains of a house in Tarawa Atoll, Kiribati, destroyed by rising sea levels and storms, exacerbated by climate change.
3- Sea level rise
Another element observed was sea level rise, which was constantly occurring. Between January 1993 and October 2023, sea level rose by more than 10 cm, reaching a record value in 2023.
Moreover, there is an acceleration, with the rate of rise in mean sea level in the last ten years more than double that recorded between 1993 and 2002.
Projections indicate that the increase will continue at a rapid and increasing rate, especially due to rising ocean temperatures and the melting of ice from glaciers and polar ice caps.
At the current rate, the melting of Greenland and Antarctica could contribute to a rise in average sea levels of about one meter this century, in a scenario characterized by rising greenhouse gas emissions.
4- The ice mass
The fourth indicator is ice mass. So-called glaciers, or glaciers, are a large mass of ice that can take up to 30 thousand years to form. They are found all over the planet, especially at the top of the highest mountains. Glaciers store 70% of the planet’s fresh water.
Since the 1970s, there has been an average decrease of more than 30 meters in the thickness of these glaciers.
In August 2023, a new altitude record was set in Switzerland for the point at which water freezes in the atmosphere, which reached 5,298 metres. This is much higher than the peaks of Europe’s highest mountains, such as Mont Blanc, which reaches 4,811 metres.
The Iceberg Tunnel was photographed at Portal Point, Antarctica
5- The extent of sea ice
The fifth measurement is the extent of sea ice. New figures show that in September this year, Antarctic sea ice reached 1.5 million square kilometrestwo Smaller than average, it is roughly the size of Portugal, Spain, France, and Germany combined.
It is good to remember that ice also has a role in reflecting sunlight, so as the ice sheet on the planet decreases, more heat is retained and this accelerates the melting of the remaining ice.
6- Ocean acidification
The sixth indicator observed is ocean acidification. The seas absorb about 23% of annual human-caused carbon dioxide emissions, but they pay a high environmental price for it.
Carbon dioxide reacts with seawater, increasing its acidity, endangering living organisms, including affecting fishing and aquaculture. This also affects coastal protection by weakening coral reefs that act as a barrier to the coast.
Air pollution from power plants contributes to global warming
7- Concentration of greenhouse gases
Finally, the composition of the atmosphere is analysed. What is most worrying in this sense is the increasing concentration of gases that cause the “greenhouse effect,” that is, they retain heat.
Emissions of these gases have risen dramatically due to human activities since the beginning of the industrial age, and this is the main reason scientists have identified for the climate changes we are seeing today.
The main greenhouse gas is carbon dioxide. Some of it is absorbed by forests and seas, but about half remains in the air and takes many years to dissipate.
The last time Earth recorded a similar concentration of carbon dioxide was 3 to 5 million years ago, when temperatures were 2 to 3 degrees Celsius warmer and sea levels were 10 to 20 meters higher than they are now.
At that time, only carbon dioxide was emitted through natural processes. Today, human-generated carbon dioxide emissions, although lower than those from natural processes, create an excess that cannot be absorbed, leading to a fatal imbalance.
Data from reference institutions
The World Meteorological Organization uses datasets from several international reference institutions and research centres, including global temperature data from six reference institutions in the field of climate monitoring.
The first of these agencies is the United States National Aeronautics and Space Administration (NASA). This agency has at least 42 satellites and space instruments dedicated to measurements related to the Earth’s climate.
The second reference organization is the US National Oceanic and Atmospheric Administration (NOAA), which owns or operates 17 satellites, 1,322 marine buoys, 15 ships, and 9 weather monitoring aircraft.
In addition, the agency organizes a database containing records from more than 100,000 meteorological stations from 180 countries and territories.
The third source of data is the Met Office, the UK’s national meteorological service, founded in 1854. The English center is a reference due to its technological capacity based on the use of supercomputers to carry out weather forecasts and climate change forecasts.
World Meteorological Organization (WMO) for North America, Central America and the Caribbean
The fourth is the European Center for Weather Forecasting, Ecmwf, which runs one of the world’s best-performing weather forecast models and the ERA5 reanalysis model, which integrates variables from the atmosphere, soil and oceans, with high spatial and temporal resolution.
The WMO’s fifth source is the Berkeley Earth Group, an independent scientific data science organization that studies trends and performs statistical analyzes and simulations with information from weather stations around the world.
The sixth source is the Japan Meteorological Agency, JMA, which developed a third-generation reanalysis model, JRA55, which was the first of its kind to make information available since the late 1950s.
Scientific consensus
Moreover, meteorology is one of the disciplines in which there has been long and successful international cooperation. Observing systems, including stations around the world, must follow and operate according to strict specifications to generate uniform, reliable and robust data.
The WMO Global Observing System currently has More than 11,000 land stations, about 4,000 on board ships, and more than 1.2,000 buoys on the sea surface send monitoring data in real time, in addition to many satellites, aircraft, radars, atmospheric electrical discharge detectors, and others.
All this sharing of information that comes from these stations and observations feeds databases and climate models used in careful studies of why the planet is currently warming.
That’s why, according to NASA, 97% of climate scientists actively developing and publishing studies agree that humans are causing global warming and climate change.
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