In the past few weeks, climate records have been broken around the world. July 4 was the hottest average day in the world, with a new record set the previous day. The mean sea surface temperature was the highest recorded, and the sea ice extent in Antarctica was the lowest recorded.

Also on July 4, the World Meteorological Organization announced the start of El Niño, which “created the conditions for a possible sharp increase in global temperatures and devastating weather and climate.” So what’s going on in the climate and why are we seeing all these records falling at the same time?

Against the background of global warming, El Niño conditions have the added effect of raising temperatures to record highs. This is combined with a reduction in aerosols, which are fine particles that can deflect incoming solar radiation. Therefore, these two factors are most likely responsible for the record heat in the atmosphere and oceans.

Not just climate change

The overheating we’re seeing is largely due to the El Niño that’s happening right now, increasing people’s warming trend caused by greenhouse gas emissions. El Nino is declared when the sea surface temperature rises significantly over much of the tropical Pacific Ocean. These higher-than-average ocean surface temperatures contribute to above-average land temperatures.

The last strong El Niño was in 2016, but we’ve since released 240 billion tons of CO₂ into the atmosphere. El Niño does not create additional heat, but redistributes existing heat from the ocean to the atmosphere.

The ocean is very big. Water covers 70% of the planet and can store large amounts of heat due to its high specific heat capacity. Therefore, your heater stays hot longer than your wheat sack. And why is 90% of the excess heat from global warming absorbed by the ocean? Ocean currents radiate heat between the Earth’s surface, where we live, and the depths of the ocean. During El Niño, the trade winds over the Pacific weaken and the rise of cold waters along the Pacific coast of South America decreases. This leads to warming of the upper layers of the ocean.

In June 2023, warmer-than-normal ocean temperatures were recorded in the first 400m of the Pacific Ocean along the equator. Because cold water is denser than warm water, this layer of warm water prevents cold ocean waters from reaching the surface. Warmer ocean waters over the Pacific also lead to more thunderstorms that release more heat into the atmosphere through a process called latent heating.

This means that the accumulated heat from global warming lurking in the ocean during the last La Niña years is now coming to the surface and then breaking records.

Absence of aerosols across the Atlantic

Another factor contributing to the unusual temperature is the reduction in aerosols.

Aerosols are tiny particles that can deflect incoming solar radiation. Injecting aerosols into the stratosphere is a potential geoengineering technique that humanity could use to mitigate the effects of global warming. Although it is much better to stop greenhouse gas emissions.

But the absence of aerosols can also increase the temperature. A 2008 study concluded that 35% of the annual variation in sea surface temperature over the Atlantic Ocean during the Northern Hemisphere summer can be explained by changes in Saharan dust. Recently, the level of Saharan dust over the Atlantic Ocean has been extremely low.

Similarly, in 2020, new international regulations regarding particulate sulfur in marine fuels were introduced, resulting in a global reduction in sulfur dioxide (and aerosol) emissions over the ocean. But the long-term benefits of reducing emissions from shipping far outweigh the relatively minor warming effect.

The combination of these factors is why global average surface temperature records are falling.

Are we at the point of no return?

In May of this year, the World Meteorological Organization announced that there is a 66% probability that the global average temperature will temporarily rise 1.5°C above pre-industrial levels over the next five years. This forecast reflected the development of El Niño. The probability is higher now that El Niño has developed. It is worth noting that a temporary exceedance of 1.5℃ according to the Intergovernmental Panel on Climate Change standards does not mean that we have reached 1.5℃. The latter describes a continuous global average temperature anomaly of 1.5°C instead of a single year, and will likely appear in the 2030s.

This temporary excess of 1.5°C will give us a sad picture of what our planet will be like in the years to come. Although younger generations dream of a nice 1.5℃, given current greenhouse gas emission policies are leading us to 2.7℃ warming by the end of the century.

So we are not at the point of no return. But the timeframe for preventing dangerous climate change is shrinking fast, and the only way to prevent it is to end our dependence on fossil fuels.