According to multiple sources – including NASA, NOAA, the Berkeley Earth Research Group and the Met Office Hadley Center (UK) – global temperatures in recent years have been some of the hottest ever recorded. This is the direct result of anthropogenic factors such as overpopulation, urbanization, deforestation and increased greenhouse gas emissions (such as carbon dioxide and methane).
According to a press release recently released by NASA, 2020 was the hottest year on record in terms of global temperatures – effectively tied to 2016 (the previous record holder). The publication includes a dramatic video showing the average rise in temperature since 1880 and the ecological crises that have only occurred in the past year. This is another warning of how human agency affects the very systems we rely on for our continued survival.
Overall, the Earth’s average temperature has risen by more than 1.2 ° C since the 1880s. According to NASA’s Goddard Institute for Space Studies (GISS) temperature analysis – known as GISTEMP – the average global temperature for 2020 was 1.02 ° C (1.84 ° F) warmer than the 1951-1980 baseline. This is in line with the long-term warming trend and places 2020 just before 2016, effectively tying the two for the warmest year in existence.
This analysis combines surface and sea temperature measurements from more than 26,000 weather stations and thousands of ship and buoy based instruments. Together with an algorithm that corrects for the different distance from temperature stations and urban warming effects, the end result is an estimate of the global mean temperatures from a base period from 1951 to 1980 – with an error rate of 0.05 ° C and a confidence level of 95%.
Cause for concern
As GISS Director Gavin Schmidt explained, annual records are nowhere near as long-term trends that have been worrying:
“The past seven years have been the warmest in seven, reflecting the continuing and dramatic warming trend. Whether a year is a record or not doesn’t really matter – the most important things are long-term trends. With these trends and the increasing human impact on the climate, we must expect records to continue to be broken. “
Global temperatures are a critical indicator of how our climate is changing over time due to the impact humanity has on the natural environment. Their mean increase over time has led to phenomena such as decreasing ice cover, rising sea levels, disappearance of water tables and drought, forest fires, persistent heat waves, increased storm activity, disease outbreaks and species extinctions.
A separate, independent analysis by the National Oceanic and Atmospheric Administration (NOAA) concluded that 2020 was the second warmest year on their record, after 2016. NOAA scientists use much of the same raw temperature data in their analysis but have a different baseline period (1901-2000) and methodology. Also, unlike NASA, NOAA does not derive temperatures in polar regions without observations, which is a large part of the difference between NASA and NOAA records.
Annual temperature anomalies (1880-2019) as recorded by NASA, NOAA, the Berkeley Earth Research Group, and the Met Office Hadley Center. Credits: NASA GISS / Gavin Schmidt
Understanding long-term climate trends is not only important to educate the public about climate change and develop solutions. This is also of crucial importance for developing crisis strategies and adapting to changing environmental conditions. This can mean growing various crops, managing water resources, and preparing for extreme weather events.
Annual trends
While the long-term trend was consistent (with the increase overall), different events will contribute to the average temperatures in a given year. Two events took place for 2020 that limited the amount of sunlight reaching the earth’s surface. The first was the Australian bushfires, which raged for months, scorching 46 million acres of land, releasing smoke and particles that were over 30 km high in the atmosphere.
This event limited the amount of sunlight reaching the lower atmosphere and likely caused a slight cooling. The second factor was the COVID-19 pandemic, which resulted in significant reductions in air pollution in certain parts of the world, bringing more sunlight to the surface (thus warming it). At the same time, the cumulative CO2 concentrations continued to increase this year and to maintain the long-term trend.
Thanks to a number of environmental factors, temperatures also vary from year to year. The largest single product is usually the El Nino-Southern Oscillation (ENSO), a naturally occurring cycle in which heat is exchanged between the ocean and the atmosphere in the central and eastern Pacific. This allows warm water and air to move from the western Pacific to the Americas, and reduces the swelling of cooler, nutrient-rich water from below.
Carbon dioxide in the earth’s atmosphere when half of global warming emissions are not absorbed. Photo credit: NASA / JPL / GSFC
This year the ENSO ended with a cool phase, but started with a slightly warm phase, which overall led to a slight increase in the average temperatures. Schmidt said:
“The previous record year 2016 was significantly boosted by a strong El Nino. The lack of similar support from El Nino this year is evidence that the background climate is continuing to warm due to greenhouse gases. “
Regional deviations
It is also important to realize that the GISS data represents surface temperatures that have been averaged over the entire planet over the entire year. This means that regional weather patterns have an impact and that the temperature deviations in 2020 were different depending on the location. This also means that certain parts of the world will warm faster than others in the long run.
For example, the GISTEMP analysis shows that the Arctic has warmed three times faster than the rest of the world in the past 30 years, which has resulted in a higher proportion of melting sea ice. The minimum area of sea ice in the Arctic is currently decreasing by around 13% annually, resulting in the region reflecting less and the ocean absorbing more sunshine.
This is the reason for “Arctic Reinforcement,” where the oceans absorb more sunlight and temperatures continue to rise, leading to even greater melting, sea level rise, loss of permafrost in the Arctic Circle and more intense Arctic forest fires. It is therefore important to understand that a global average increase of just a few degrees does not mean that the warming trend does not matter.
For more information about NASA’s full surface temperature dataset and the methodology they use, visit NASA’s GISS Surface Temperature Anaylsis website.
Further reading: NASA
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