The world crosses 2-degree warming limit for first time: What does it mean?

In September, the world passed 1.5 degrees Celsius of warming. Two months later, we hit two degrees Celsius of warming. It’s fair to wonder what is going on. What we’re seeing is not runaway climate change. These are daily spikes, not the long-term pattern we would need to say the world is now two degrees hotter than it was in the pre-industrial period. These first breaches of temperature limits are the loudest alarms yet. They come as the United Nations Environment Programme warns the world is still on a path to a “hellish” three degrees Celsius of warming by the end of the century. But they do not signal our failure. The sudden spike in warming in 2023 comes from a combination of factors – climate change, a strong El Niño, sea ice failing to reform after winter, reduced aerosol pollution and increased solar activity. There are also minor factors such as the aftermath of the volcanic eruption near Tonga.

Final numbers out from @CopernicusECMWF for the 17 Nov temperature anomaly at

2.07°C above preindustrial and

Provisional data for 18th Nov at

2.06°C above preindustrial

Now two Nov 2023 days where global temperature exceeded 2°C in ERA5

💙💙🩵💙🩵🤍🧡❤️❤️❤️💔#COP28 https://t.co/Cc0PK3K9FW

— Dr Sam Burgess 🌍🌡🛰 (@OceanTerra) November 20, 2023

How important are these factors? 1. Climate change This is by far the biggest factor. What many of us don’t recognise is how recent our intense period of emissions is. If you were born in 1983, fully 50 per cent of all of humanity’s emissions have gone into the atmosphere since your birth. Human emissions and other activities have  so far contributed about 1.2 degrees Celsius of warming. Greenhouse gases trap heat, which is why the Earth is not a snowball. But the two trillion tonnes of fossil carbon we’ve taken from underground and put back in the atmosphere are trapping more heat. And more heat. And will continue to do so until we stop burning fossil fuels for heat or power. 2. El Niño The El Niño-Southern Oscillation climate cycle in the Pacific has the biggest natural influence on climate. That’s because the Pacific is huge, accounting for 30 per cent of Earth’s surface. When in the El Niño phase, the seas off South America heat up. This, in turn, usually makes average global temperatures hotter. Right now, there’s a dangerous heatwave in Brazil, where heat and humidity combined makes it  feel like 60 degrees Celsius. The intense heat contributed to the  death of a fan at Taylor Swift’s Rio concert last week. El Niño will likely peak in the next two months. But its effects may well persist throughout 2024, driving global average temperatures higher by perhaps 0.15°C. 3. Antarctic sea ice isn’t bouncing back The declines in Arctic sea ice are well known. But now Antarctic sea ice, too, is  failing to recover. Normally, the ring of frozen seawater around the ice continent reaches maximum extent in September. But this year’s maximum is well below any previous year. [caption id=“attachment_13413832” align=“alignnone” width=“640”] Blocks of ice drift on the water off the coast of Collins glacier on King George Island in Antarctica. AFP[/caption] As we enter summer, that means more dark water will be exposed. And since dark surfaces absorb more heat while white ones reflect it, it means still more heat will go into the oceans rather than back out to space. 4. Increased solar activity Our Sun runs on a roughly 11-year cycle, going between lower and higher output. The solar maximum was forecast for 2025 and a clear increase is occurring this year. This brings spectacular auroras – even in the Southern Hemisphere, where residents have seen auroras  as far inland as Ballarat, in Victoria. Solar maximums add extra heat. But not much – the effect is only  around 0.05 degrees Celsius, about a third of an El Niño. 5. Volcanic eruption Normally, volcanic eruptions cool the planet, as their vast plumes of aerosols block sunlight. But the largest volcanic eruption this century near Tonga in January 2022 did the opposite. That’s because the Hunga Tonga-Hunga Ha’apai volcano was under the sea. Its explosive force evaporated vast volumes of seawater – and water vapour is a greenhouse gas. While some sceptics like to point to this eruption as the root cause of our recent spike in warming, the Tonga eruption is a blip – it will add an  estimated 0.035 degrees Celsius for about five years. 6. Reducing aerosol pollution In 2020, new international shipping rules came into force, mandating low-sulphur fuels. This cut sulphur dioxide emissions by about 10 per cent. That’s good for health. But aerosols in the atmosphere can actually block heat. Cutting pollution may have added to warming. But again, the effect seems small, adding an estimated 0.05 degrees Celsius of warming by 2050. [caption id=“attachment_13413892” align=“alignnone” width=“640”] Smoke billows from chimneys at chemical factories on the outskirts of Nanjing, Jiangsu province. Reuters[/caption] What can we learn from this? The climate is enormously complex. We should see the first day two degrees Celisus warmer than the same day in the pre-industrial period as a stark warning – but not as a sign to give up. In short, this isn’t a step change. It’s a combination of factors which has driven this surge. Some of those, like El Niño, are cyclical and will switch back. But as negotiators prepare for next week’s COP28 climate talks, it’s yet another sign that we cannot relent. We are – at last – seeing signs of real progress in the clean energy and clean transport roll out. This year, we may even see emissions from power generation  finally peak and then begin to fall. So – we haven’t failed, yet. But we are on a rapidly warming planet – and we can now clearly see the effect, even in these new daily temperature records. This article is republished from  The Conversation under a Creative Commons license. Read the  original article.