Global Warming, Ocean Current and Heatwave

Global warming is happening at an unusually fast rate, meaning the earth’s average surface temperature is rising. It disrupts the global ocean conveyor belt by altering water density. Melting ice and increased rainfall introduce freshwater into polar regions. This makes surface water lighter, preventing it from sinking, thereby slowing critical currents like the Atlantic Meridional Overturning Circulation (AMOC). Ocean currents act as the earth’s global conveyor belt, distributing immense amounts of solar heat from the equator towards the poles. When AMOC slows down, stalls or gets disrupted, it causes localised heat buildups. This triggers "marine heatwaves"-- periods of 

prolonged, extreme ocean temperatures that disrupt ecosystems and fuel severe terrestrial heatwaves.

The UK is currently facing an extreme heatwave. Author Bill McGuire, in his book “The Fate of the World: A History and Future of the Climate Crisis”, mentioned that UK temperatures may touch forty degrees celsius this year and/or next. McGuire further added that ‘especially with the strongest El Niño on record building in the Pacific, in fact, temperatures as high as forty-five degrees are now possible.’ El Niño is a natural Pacific weather pattern that pushes up global temperatures and is likely to emerge this summer. In fact, this week, parts of England and Wales reached thirty-eight degrees Celsius. Amber extreme heat warnings have been put in place for the east and southeast of England and parts of the southwest of England and Wales.

Recent research published in the Advances in Climate Change Research mentioned that the unprecedented loss of ice across the Pamir Mountains of Asia has been observed. Before 2022, the ice mass of the glacier exhibited some fluctuation, but since then, ice loss has been accelerated. Research suggests that in 2025, a record high loss of ice, equivalent to the entire surface of the glacier losing 1.5 metres of water, will occur. This is four times higher than the glacier’s average loss during 2011-2024. The findings suggest that the glaciers of the Parim-Karakoram region are no longer an exception to the global trend, and extreme events are likely to further accelerate glacier melt there.

There is a vicious circle between heatwaves and greenhouse gas. Heatwaves can lead to wildfires. In the Arctic, plants grow slowly, but their remains can accumulate in soil in forms such as peat, building up over centuries and millennia. This means soils in the Arctic and in the boreal forests nearby have been acting as a carbon sink. But research suggests that with fires becoming more frequent in the Arctic region, rapid burning of the surface vegetation is triggering the release of lots of soot or black carbon, as well as carbon dioxide. The Finnish Meteorological Institute, based in Helsinki, mentioned that ‘soil combustion could unlock long-stored carbon from soils that have been considered previously as carbon sinks.’ It is clear that because of global warming and heatwaves, we are moving into new fire regimes that are destroying the topsoil layers and also burning peatlands and releasing old carbon from the soil.

Research published in the Science journal suggests that forest fires can release carbon monoxide, but it can also be released from fossil fuel use. These compounds and various volatile organic compounds react with other compounds in the atmosphere to form ozone. This ozone is not the same as naturally occurring ozone in the upper stratosphere. In the upper stratosphere, ozone filters harmful ultraviolet rays, whereas ozone formed in the lower atmosphere traps heat that would otherwise radiate to space. The indirect greenhouse gases also warm the planet by reacting with hydroxyl radicals. For example, if more hydroxyl reacts with carbon monoxide and volatile organic carbon, then less will be available to break down methane. This means more methane in the atmosphere, which can trap eighty times more heat than carbon dioxide.

Another issue is the amount of light that earth reflects and its nature of reflection. It is known to us that the northern and southern hemispheres have almost equal reflectivity or albedo, where albedo is the measure of how much light, specifically solar radiation, is reflected by a surface. This means that a line that runs through Africa, Europe, Alaska and both poles divide Earth into two halves that reflect the same amount of light. But recent research carried out by the National Oceanic and Atmospheric Administration (NOAA) suggests that there is a second line of symmetry along the twenty-seven-degree east and one hundred fifty-three-degree west meridians. NOAA’s research published in the Nature journal informed us that hemispheres separated by this second line are equal in three respects: their albedo in clear skies, the reflectivity of clouds and the fractions covered by ice-free oceans. Researchers from the Centre for International Climate Research in Oslo suggest that it is likely that this is a ‘robust feature and potentially another fascinating property of Earth’. This symmetry issue may be connected to one of the most important modes of climate variability on earth.

There  is a huge uncertainty in climate models about the fate of the future AMOC. In its sixth assessment report, the Intergovernmental Panel on Climate Change (IPCC) said that while it was confident the AMOC would decline over the rest of this century, it had ‘medium confidence’ that it would not collapse before 2100. A study published in 2025 in the journal Geophysical Research Letters found that if AMOC collapses, then cold extremes could reach minus twenty degrees Celsius in London and minus forty-eight degrees Celsius in Oslo. Any weakening of the AMOC risks pushing the system past an unknown tipping point threshold. It is difficult to know where the threshold lies. Another research publication in the Environmental Research Letters suggests that AMOC shutdown can occur in sixty-seven per cent of cases under high emissions and thirty per cent under the medium-emission scenario. There is a big uncertainty about where the critical ocean system is heading. There could be other key processes yet to be incorporated in the model to understand the behaviour of AMOC.

In short, instead of finding out who to blame, it is imperative to understand carefully what is happening in nature and its cause and effect. This will allow us to make some rational and pragmatic decisions regarding global warming and climate change. So, we should embrace Aesop’s advice, ‘Look before you leap’.