Recent spikes in and average have left climate scientists across the world scrambling to find the cause. The global average air temperature, relative to 1850-1900, exceeded the 1.5℃ lower during part of March and the first days of June. This last happened in 2020, and before that during the powerful .
Author
Steve Turton
Adjunct Professor of Environmental Geography, CQUniversity Australia
What makes these most recent temperature spikes so alarming is that they’ve occurred before a forecast in the Pacific, rather than during one.
It is now clear that Earth’s climate system is way out of kilter and we should be very concerned.
We already know El Niño events are associated with . Given the , we all need to take extra notice of what lies ahead for the next few years. This is especially so as this forecast warming event will follow the recent rare triple La Niña event that usually brings , meaning the trajectory of this year’s uptick in average temperatures is likely to be even steeper.
The – the difference between the amount of energy arriving from the Sun and the amount returning to space – is now running at an all-time high. This is the most of the prospects for continued global heating and human-driven climate change.
This metric will also be vital for monitoring our overall success in meeting the Paris Agreement’s targets, which call for humanity to hold average warming ideally to 1.5℃ above the pre-industrial average, or at least to as much under 2℃ as possible.
How much warmer are the oceans this year?
, about 89 % of the excess heat in Earth’s climate system has been stored in the ocean (with 6 % on land, 1 % in the atmosphere, and about 4 % going towards melting ice on land and sea).
Because of this, any significant upward trend in average ocean heat is considered a harbinger for the acceleration of human-driven climate change more generally.
Scientists monitor the status of Earth’s energy imbalance by considering how much the differs from the historical average, for a vast slice of the oceans covering everywhere between the Arctic Circle (60°N) and Antarctic Circle (60°S). These “sea surface temperature anomalies” are calculated each month, relative to the 1971-2000 baseline.
The global sea surface temperature anomaly on June 13 was about 4.5 above the baseline global average. Put another way, this means the likelihood of current temperatures happening totally at random, if the climate this month was unchanged from the baseline period, are about 1 in 1.2 million.
This anomaly is so far above record levels it is to a have occurred in a climate without .
The 36-month for the Earth Energy Imbalance is now at a record 1.36 Watts per square metre. This looks like a small value, but it corresponds to an average of 11 Hiroshimas of excess energy per second accumulating in Earth’s climate system over the past three years.
Why is this happening now?
A range of are behind this record global energy imbalance. These include rapidly declining and unusually warm temperatures in .
The early arrival of El Niño may also be playing a lesser role, as the warming in the central and eastern equatorial Pacific is not expected to peak until next year.
The submarine volcano erupted in January 2022 and ejected record-breaking amounts of water vapour into the stratosphere. Water vapour acts as a , and this may be contributing to the .
Other possible agents of warming include new regulations around from shipping, and even a recent . Both these forms of have a cooling effect, as they reflect a small percentage of sunlight back to space.
are not restricted to the Pacific. The at present. In fact, the entire North Atlantic has broken for any time of year.
This pool of warm water has been linked to , creating a over eastern Canada and providing a catalyst for .
If a strong El Niño develops later this year and continues in 2024-25, it will bring a very high risk of .
There is also a the will occur over the next five years.
Eastern Australia is an . This means an for drought, bushfires, heatwaves, crop failures and mass coral bleaching events on the .
from human sources continue to rise and accumulate in the atmosphere. Rising emissions will fuel global heating, resulting in – what is often termed the “new normal” brought about by climate change.
Climate models predict with high certainty that as these climate baselines shift, so will the increased risk of . Effects of natural climate drivers, such as patterns in the Pacific, are as the background climate warms.
Scientists will watch the current spike in global ocean and atmospheric temperatures very closely as the forecast El Niño strengthens later this year. What is less well understood is how other climate drivers may interact with the warming effects of El Niño.
Notably, how will the lingering atmospheric water vapour from the Hunga Tonga-Hunga Ha’apai eruption amplify any El Niño warming? All we can do is prepare for more record-breaking weather.
Steve Turton has previously received funding from the Australian Government. Steve is the vice chair of the Australian Citizen Science Association.
