The warming of planet earth cannot be understood without first grasping ocean warming. Don’t think about warming in terms of rising temperatures. Instead, think of it in terms of increasing heat content. More than 90 percent of the extra heat absorbed by planet earth over the past 50 years ended up in the oceans.
The oceans do redistribute heat via large-scale circulatory currents. However, redistributing heat does not mean it goes away. The redistribution spreads heat energy across the planet. That energy will move from warmer to colder latitudes and from surface waters to deeper ocean waters.
Over long periods of time, the energy from ocean warming seeks various ways to dissipate. Melting ice, evaporating water, and transfering back into the atmosphere are all ways that mother nature solves a heat imbalance. Heat absorbed in the oceans today takes decades before being fully integrated back into the earth’s web of energy.
The origins of heat
The primary source of heat for warming earth’s oceans is the sun. Remember that the oceans cover about 71 percent of the planet’s surface. Dark ocean waters are poor reflectors of sunlight but excellent absorbers of solar energy. The oceans also act as a buffering system for the atmosphere when they absorb heat trapped by greenhouse gases.
Solar heat has entered the oceans for millions of years. So, why has it become a problem now? Earth’s heat budget has changed due to the rise in greenhouse gas concentrations. Before this rise, heat from the sea was transferred to the atmosphere and radiated back into space at a relatively consistent rate. Now, a thicker blanket of greenhouse gases interrupt this process and trap more heat at the earth’s surface.
Rising levels of greenhouse gases and ocean warming are a bit of a tag-team act.
How much heat?
The graph above is from NOAA, and it shows heat content in the world’s oceans for just over 60 years (Heat content increases upward). About 180 sextillion joules of heat entered the world’s oceans over this time period (180,000,000,000,000,000,000,000 joules). This amount of energy is equivalent to the energy released by 2.8 billion Hiroshima sized atomic bombs, or about three bombs exploding every 2 seconds for 63 years. Now, the most recent research places the number at 3.6 billion bombs. We won’t quibble over a mere 0.8 billion atomic bombs, because the numbers are already incomprehensible in terms of human experience.
Two aspects of the graph are worth noting. Firstly, is the acceleration in heat absorption about halfway through the cycle in 1985. About 20% of the heating occurs in the first thirty years, and the remaining 80% occurs in the last 30 years. The heating rate is four times faster now than in the first 30 years of the cycle.
The second thing to note is that the oceans are vast. The energy equivalent of 2.8 billion atomic bombs raised the average surface temperature of the oceans by about 1 degree Fahrenheit. However, this seemingly small temperature rise should not be interpreted as a dismissal of the climate implications. Instead, it is an affirmation of the stupendous amount of heat energy contained in that 1 °F change. That heat can melt a lot of ice.
Climate change: Ocean Heat Content (By LuAnn Dahlman and Rebecca Lindsey – NOAA) – https://www.climate.gov/news-features/understanding-climate/climate-change-ocean-heat-content Also:
Ocean warming, explained (By ALEJANDRA BORUNDA – National Geographic) – https://www.nationalgeographic.com/environment/oceans/critical-issues-sea-temperature-rise/ Also:
In 2019, Oceans Were Hotter Than at Any Other Point in Recorded History (By Rosie McCall – Newsweek) – https://www.newsweek.com/2019-oceans-hotter-any-point-recorded-history-1481895 Also:
Climate Change Indicators: Sea Surface Temperature (EPA) – https://www.epa.gov/climate-indicators/climate-change-indicators-sea-surface-temperature Also:
Feature Image: DOMINICAN REPUBLIC. Desert island (By Ronald Saunders) (Modified) – This file is licensed under the Creative Commons Attribution-Share Alike 2.0 Generic license. – https://creativecommons.org/licenses/by-sa/2.0/deed.en Also: