Explained: Why was 2020 one of the hottest years on record?

2020 has been recorded as one of the hottest years by various agencies. While NASA’s Goddard Institute for Space Studies says that 2020 was the hottest year on record tying with 2016 (which held the previous record for the hottest year), the US NOAA’s National Centers for Environmental Information has said that 2020 was the second warmest year on record since 1880, when it started maintaining records.

These agencies report their measurements of the Earth’s surface temperatures in January every year. Last year, 2019 was declared to be the second warmest year ever by the European weather agency’s Copernicus climate change programme. The Indian Meteorological Department (IMD) has said that 2019 was the seventh warmest year for the country last year.

According to NOAA, the average temperature across global land and ocean surfaces for 2020 was 0.98 degree Celsius above the average for the 20th century and just 0.02 degree Celsius less than the average temperature for 2016. Significantly, the seven warmest years on Earth have occurred since 2014 and the 10 warmest have occurred since 2005.

Further, as per Berkeley Earth’s Global Temperature Report for 2020, it has been referred to as the second warmest year on Earth since 1850. But as per their analysis, the difference in temperatures between 2016 and 2020 comes out to 0.022 degree Celsius. Therefore, both years could be regarded as effectively tied.

What does this mean?

As per NOAA, some of the significant climate anomalies and events of 2020 include cyclone Amphan, the second super cyclone to form over the Bay of Bengal in two decades. The cyclone made landfall between Digha, which is about 180 km south of Kolkata in West Bengal, and Hatiya islands in Bangladesh during the afternoon to evening hours of Wednesday, May 20, 2020, with the maximum sustained wind speed of 155-165 kmph gusting to 190 kmph.

Other events include hurricanes Eta and Iota, which made landfall as category four storms within 25 km of each other in Nicaragua. An example of extreme events in the US is of the wildfires that ravaged California. Out of six of the largest wildfires in California recorded since 1932, five occurred in 2020. The smoke and ash from these fires gave the skies around the San Francisco Bay area and in some parts of Oregon and Washington an orange hue and also affected the air quality in these areas.

As per the California Department of Forestry and Fire Protection (CAL FIRE), while wildfires are a natural part of the state’s landscape, the fire season in the state and across the Western US is starting earlier and ending later each year. Even so, scientists have been wary of attributing any single contemporary event to climate change, because of the difficulty in completely ruling out the possibility of the event having been caused by some other reason or due to natural variability.

Similarly, the Australian bushfires that started in 2019 lasted into early 2020 and were unprecedented in scale. These fires were seen as one of the biggest climate disasters of the past few years.

NASA has said that decades of greenhouse gas emissions set the stage for this year’s events and that human-produced greenhouse gas emissions are largely responsible for warming the Earth. These activities include burning fossil fuels such as coal, oil and natural gas, which release greenhouse gases forming an insulating blanket, which traps heat near the Earth’s surface.

Significantly, NASA notes that carbon dioxide levels have increased by over 50 percent since the Industrial Revolution began 250 years ago, while the level of methane has more than doubled. This has warmed the Earth by about 1 degree Celsius since this period.