Temperatures in polar regions have risen strongly, so leaving out the rise in polar regions would downplay the global temperature rise since pre-industrial. A recent analysis of the temperature rise therefore uses an adjustment of 0.1°C to compensate for missing data.
Ocean heat on the Northern Hemisphere is driving up temperatures in the Arctic.
The image below shows that the April ocean temperature anomaly in the Gulf of Mexico in 2020 was 1.71°C or 3.08°F higher than the 1910-2000 average, and the highest on record.
There are three reasons why this is very worrying:
1. The Gulf Stream carries ever hotter water along the path of the Gulf Stream toward the Arctic Ocean, thus speeding up the temperature rise of the Arctic Ocean.
2. As the Gulf Stream slows down, due to increased meltwater, more heat is accumulating along the path toward the Arctic Ocean, threatening to invade the Arctic Ocean in abrupt strong bursts, powered by stronger winds over the North Atlantic, as discussed in earlier posts such as this one.
3. There's also the danger that a freshwater lid is extending at the surface of the North Atlantic that threatens to cause more ocean heat to move underneath the sea surface toward the Arctic Ocean, as discussed in earlier posts, such as at this one and this one.
As the image below shows, the April ocean temperature anomaly on the Northern Hemisphere in 2020 was 0.97°C or 1.75°F higher than the 20th century average, and the highest on record.
Arctic sea ice is getting very thin and, at this time of year, it is melting rapidly from below, due to rising temperature of the Arctic Ocean.
An earlier analysis indicates that there is a tipping point at 1°C at which the sea ice underneath the surface of the Arctic Ocean disappears, which means that there will be little or no buffer left to consume the influx of ever warmer and salty water from the Atlantic Ocean and Pacific Ocean.
As long as there is sea ice in the water, this sea ice will keep absorbing heat as it melts, so the temperature will not rise at the sea surface.
But there is ever less sea ice volume left to absorb ocean heat, and the amount of energy absorbed by melting ice is as much as it takes to heat an equivalent mass of water from zero to 80°C.
Meanwhile, global heating continues and more than 90% of global heating is going into oceans.
As the temperature of the oceans keeps rising, more heat will reach sediments at the seafloor of the Arctic Ocean that contain vast amounts of methane, as discussed in this page and this post. The danger is that this heat will destabilize the ice and the hydrates, resulting in huge releases of methane.
The situation is dire and calls for immediate, comprehensive and effective action, as described in the Climate Plan.
• NASA GISS maps - Land Surface Air Temperature and Sea Surface Temperature
• Crossing the Paris Agreement thresholds
• NOAA Global Climate Report - April 2020
• NOAA ocean heat content
• Arctic Hit By Ten Tipping Points
• Why stronger winds over the North Atlantic are so dangerous
• Why America should lead on climate
• Methane's Role in Arctic Warming
• Critical Tipping Point Crossed In July 2019
• The Threat
• When will we die?
• Climate Plan