2020: Hottest Year On Record

NASA data show that 2020 was the hottest year on record.

The image below shows that high temperature in 2020 hit Siberia and the Arctic Ocean.

In above images, the temperature anomaly is compared to 1951-1980, NASA’s default baseline. When using an earlier baseline, the data need to be adjusted. The image below shows a trendline pointing at an 0.31°C adjustment for a 1900 baseline. 

Additional adjustment is needed when using a 1750 baseline, while it also makes sense to add further adjustment for higher polar anomalies and for air temperatures over oceans, rather than sea surface water temperatures. In total, a 0.78°C adjustment seems appropriate, as has been applied before, such as in this analysis. For the year 2020, this translates in a temperature rise of 1.8029°C versus the year 1750.

Three trends: blue, purple and red

Will the global temperature rise to 3°C above 1750 by 2026? The blue trend below is based on 1880-2020 NASA Land+Ocean data and adjusted by 0.78°C to reflect a 1750 baseline, ocean air temperatures and higher polar anomalies, and it crosses a 3°C rise in 2026.

The trend shows a temperature for 2020 that is slightly higher than indicated by the data. This is in line with the fact that we’re currently in a La Niña period and that we’re also at a low point in the sunspot cycle, as discussed in an earlier post. The blue trend also shows that the 1.5°C treshold was already crossed even before the Paris Agreement was accepted. 

The second (purple) trend is based on a shorter period, i.e. 2006-2020 NASA land+ocean (LOTI) data, again adjusted by 0.78°C to reflect a 1750 baseline, ocean air temperatures and higher polar anomalies. The trend approaches 10°C above 1750 by 2026. The trend is based on 15 years of data, making it span a 30-year period centered around end 2020 when extended into the future for a similar 15 year period. The trend approaches 10°C above 1750 in 2026.

The trend is displayed on the backdrop of an image from an earlier post, showing how a 10°C rise could eventuate by 2026 when adding up the impact of warming elements and their interaction.

The stacked bars are somewhat higher than the trend. Keep in mind that the stacked bars are for the month February, when anomalies can be significantly higher than the annual average.

Temperature rise for February 2016 versus 1900.

In the NASA image on the right, the February 2016 temperature was 1.70°C above 1900 (i.e. 1885-1914). In the stacked-bar analysis, the February 2016 rise from 1900 was conservately given a value of 1.62°C, which was extended into the future, while an additional 0.3°C was added for temperature rise from pre-industrial to 1900.

Later analyses such as this one also added a further 0.2°C to the temperature rise, to reflect ocean air temperatures (rather than water temperatures) and higher polar anomalies (note the grey areas on the image in the right).

Anyway, the image shows two types of analysis on top of each other, one analysis based on trend analysis and another analysis based on a model using high values for the various warming elements. The stacked-bar analysis actually doesn’t reflect the worst-case scenario, an even faster rise is illustrated by the next trend, the red line.

The third (red) trend suggests that we may have crossed the 2°C treshold in the year 2020. The trend is based on a recent period (2009-2020) of the NASA land+ocean data, again adjusted by 0.78°C to reflect a 1750 baseline, ocean air temperatures and higher polar anomalies.

Of the three trends, the red trend is based on the shortest period, and it does indicate that we have aready crossed the 2°C treshold and we could be facing an even steeper temperature rise over the next few years.

We’re in a La Niña period and we’re also at a low point in the sunspot cycle. This suppresses the temperature somewhat, so the 2020 temperature should actually be adjusted upward to compensate for such variables. Importantly, while such variables do show up more when basing trends on shorter periods, the data have not be adjusted for this in this case, so the situation could actually be even worse. 

At a 3°C rise, humans will likely go extinct, while most life on Earth will disappear with a 5°C rise, and as the temperature keeps rising, oceans will evaporate and Earth will go the same way as Venus, a 2019 analysis warned. 

James Hansen confirms that the temperature rise is accelerating, and he points at aerosols as the cause. However, most cooling aerosols come from industries such as smelters and coal-fired power plants that have hardly reduced their operations in 2020, as illustrated by the image below, from the aerosols page. 

Above image shows that on December 17, 2020, at 10:00 UTC, sulfate aerosols (SO₄) were as high as 6.396 τ at the green circle. Wind on the image is measured at 850 hPa.

Could the land sink be decreasing? A recent study shows that the mean temperature of the warmest quarter (3-month period) passed the thermal maximum for photosynthesis during the past decade. At higher temperatures, respiration rates continue to rise in contrast to sharply declining rates of photosynthesis. Under business-as-usual emissions, this divergence elicits a near halving of the land sink strength by as early as 2040. While this is a frightening prospect, it still doesn’t explain why 2020 turned out to be the hottest year on record. 

Oceans are taking up less heat, thus leaving more heat in the atmosphere. The danger is illustrated by the image below. 

The white band around -60° (South) indicates that the Southern Ocean has not yet caught up with global warming, featuring low-level clouds that reflect sunlight back into space. Over time, the low clouds will decrease, which will allow more sunlight to be absorbed by Earth and give the world additional warming. A recent study finds that, after this ‘pattern effect‘ is accounted for, committed global warming at present-day forcing rises by 0.7°C. While this is very worrying, it still doesn’t explain why 2020 turned out to be the hottest year on record. 

Ocean stratification contributes to further surface warming, concludes another recent study: 

“The stronger ocean warming within upper layers versus deep water has caused an increase of ocean stratification in the past half century. With increased stratification, heat from climate warming less effectively penetrates into the deep ocean, which contributes to further surface warming. It also reduces the capability of the ocean to store carbon, exacerbating global surface warming. Furthermore, climate warming prevents the vertical exchanges of nutrients and oxygen, thus impacting the food supply of whole marine ecosystems.”

“By uptaking ~90% of anthropogenic heat and ~30% of the carbon emissions, the ocean buffers global warming. [The] ocean has already absorbed an immense amount of heat, and will continue to absorb excess energy in the Earth’s system until atmospheric carbon levels are significantly lowered. In other words, the excess heat already in the ocean, and heat likely to enter the ocean in the coming years, will continue to affect weather patterns, sea level, and ocean biota for some time, even under zero carbon emission conditions.”

Many feedbacks are starting to kick in with greater ferocity, with tipping points threatening to get crossed or already crossed, such as the latent heat tipping point, i.e. loss of the ocean heat buffer, as Arctic sea ice keeps getting thinner. As the above map also shows, the temperature rise is hitting the Arctic Ocean particularly hard. At least ten tipping points are affecting the Arctic, including the latent heat tipping point and the methane hydrates tipping point, as illustrated by the image below.

 

[ from an earlier post ]

A combination of higher temperatures and the resulting feedbacks such as stronger ocean stratification, stronger wind, decline of Arctic snow and ice and a distorted Jet Stream is threatening to cause formation of a lid at the surface of the North Atlantic Ocean that enables more heat to move to the Arctic Ocean. This could cause huge amounts of methane to erupt from the seafloor, thus contributing to cause the 1,200 ppm CO₂e cloud tipping point to get crossed, resulting in an extra 8°C rise, as an earlier post and a recent post warned.

Dangerous acceleration of the temperature rise

The danger is that methane is erupting in the Arctic from the seafloor and that this increasingly contributes to methane reaching the stratosphere. 

While methane initially is very potent in heating up the atmosphere, it is generally broken down relatively quickly, but in the atmosphere over the Arctic, there is very little hydroxyl to break down the methane. 

Methane also persists much longer in the stratosphere, which contributes to its accumulation there. 

Large amounts of methane may already be erupting from the seafloor of the Arctic Ocean, rising rapidly and even reaching the stratosphere. 

This danger is getting little public attention. The NOAA image on the right shows the globally-averaged, monthly mean atmospheric methane abundance derived from measurements from marine surface sites. Measurements that are taken at sea level do not reflect methane very well that is rising up from the seafloor of the Arctic Ocean, especially where the methane rises up high in plumes. 

Satellite measurements better reflect the danger. The image on the right shows that the MetOp-1 satellite recorded peak methane levels as high as 2715 ppb at 469 mb on the morning of January 6, 2021. 

Most of the high (magenta-colored) levels of methane are located over oceans and a lot of them over the Arctic Ocean. 

The next image on the right shows the situation closer to sea level, at 586 mb, where even less of the high levels of methane show up over land, indicating that the methane originated from the seafloor. 

The third image on the righ shows the situation even closer to sea level, at 742 mb, and almost all high levels of methane show up over the Arctic Ocean and over areas where the Atlantic Ocean and the Pacific Ocean border on the Arctic. 

Because methane is lighter than air and much lighter than water, methane erupting from the seafloor will quickly rise up vertically. While much of the methane that is released from the seabed can get broken down in the water by microbes, methane that is rising rapidly and highly concentrated in the form of plumes will leave little opportunity for microbes to break it down in the water column, especially where waters are shallow,
as is the case in much of the Arctic Ocean.

As methane hydrates destabilize, methane will erupt with an explosive force, since methane is highly compressed inside the hydrate (1 m³ of methane hydrate can release 160 m³ of gas). Such eruptions can destabilize further hydrates located nearby. Because of this explosive force, plumes of methane can rise at high speed through the water column. 

Because methane is so much lighter than water, large methane releases from the seafloor will form larger bubbles that merge and stick together, developing more thrust as they rise through the water.

Because of this thrust, methane plumes will keep rising rapidly after entering the atmosphere, and the plumes will more easily push away aerosols and gases that slow down the rise in the air of methane elsewhere, such as where methane is emitted by cows.