We study ocean temperatures. The Earth just broke a heat increase record

By John Abraham
‘The clear, persistent rise over the past three to four decades is unmistakable evidence of an Earth that is out of balance.’
‘The clear, persistent rise over the past three to four decades is unmistakable evidence of an Earth that is out of balance.’ Photograph: Robyn Beck/AFP/Getty Images

I was fortunate to play a small part in a new study, just published in the journal Advances in Atmospheric Sciences, which shows that the Earth broke yet another heat record last year. Twenty-three scientists from around the world teamed up to analyze thousands of temperature measurements taken throughout the world’s oceans. The measurements, taken at least 2,000 meters (about 6,500ft) deep and spread across the globe, paint a clear picture: the Earth is warming, humans are the culprit, and the warming will continue indefinitely until we collectively take action to reduce greenhouse gas emissions.

We used measurements from the oceans because they are absorbing the vast majority of the heat associated with global warming. In fact, more than 90% of global warming heat ends up in the oceans. I like to say that “global warming is really ocean warming”. If you want to know how fast climate change is happening, the answer is in the oceans.

But this paper was not merely an academic exercise. It has tremendous consequences to society and biodiversity on the planet. As oceans warm, they threaten sea life and the many food chains that originate in the sea. Warmer ocean waters make storms more severe. Cyclones and hurricanes become more powerful; rains fall harder, which increases flooding; storms surges are more dangerous; and sea levels rise (one of the major causes of rising sea levels is the expansion of water as it heats).

How much did the world’s oceans warm in 2021 compared with the previous year? Well, our data shows that oceans heated by about 14 zettajoules (a zettajoule is 1,000,000,000,000,000,000,000 joules of energy). This is a mind-bending number, so it may help to use analogies. This is the equivalent of 440bn toasters running 24 hours a day, every day of the year. Another way to think about this is that the oceans have absorbed heat equivalent to seven Hiroshima atomic bombs detonating each second, 24 hours a day, 365 days a year. I have plotted the ocean heat, measured since the late 1950s, and the clear, persistent rise over the past three to four decades is unmistakable evidence of an Earth that is out of balance.

The oceans are vast, and you need many measurements spread out across the planet to get a good sense of what is happening to the oceans as a whole. This study used hi-tech temperature sensors on autonomous buoys that rise and fall in the ocean waters as they make measurements. These sensors then send the data to laboratories around the world for analysis. In addition, we deployed high-quality temperature sensors from ships, temperatures from stationary buoys, and even strapped sensors to animals so we could measure temperatures from the water they traveled through. Our research was enabled by thousands of in-field researchers who are obtaining and processing the raw data. Without their contribution, studies like this would not be possible.

We discovered that the temperatures are not rising uniformly across the planet. We found the fastest warming in the Atlantic, Indian and northern Pacific Oceans. In our work we also explore the question of why this pattern is emerging the way it is. Using climate model simulations, we directly tie various features of the ocean to human emissions of industrial pollution and greenhouse gases. These findings suggest that a similar pattern is likely to persist into the coming decades.

The information we used is absolutely crucial for understanding the planet. You could say that we took the Earth’s temperature – and the Earth’s fever is getting worse.

I asked my colleague Alexey Mishonov, a research scientist at the University of Maryland, about the implications of these findings. “Our results demonstrated that ocean warming is extensively penetrating deeper layers of the ocean,” Dr Mishonov said. “The resulting increase of the ocean heat content cannot be adequately assessed without real measurements. We need to continue our field missions and collect these data.”

My new year’s resolution is to help the planet cool down. It’s getting hot in here and there is no sign things are going to change anytime soon. Collectively, we certainly have the technology to reduce greenhouse gases, but we have never really shown the will.

  • John Abraham is a professor of thermal sciences at the University of St Thomas in Minnesota


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