The world’s oceans have been heating to unprecedented levels in recent months, with some scientists debating whether the climate is changing beyond expectation.
The Met Office told FactCheck that the trends show “our climate is now in uncharted territory” and that “human activities are warming the climate at a rate that is unprecedented in at least the last 2,000 years”.
What’s been happening
Canada has seen the worst wildfires in its history this year already, as a period of prolonged drought combined with a heatwave.
This mirrors similarly high wildfire numbers across Europe as drought grips many parts of the world. But it broadly reflects what models predict in a rapidly warming climate — more climate impacts and extreme weather.
The heating in the world’s oceans has taken scientists by surprise, however.
Across the North Atlantic in April and May, sea surface temperatures rose to record highs dating back to 1850. This peaked last week when waters around the UK were 5 degrees celsius higher than normal for this time of year, as experts declared a marine heatwave.
Part of the reason for this is thought to be natural variations in the world’s climate systems. The UN recently said it’s likely that the world is already in an El Niño phase — a natural climate pattern where sea surface temperatures temporarily rise, especially in the tropical central and eastern parts of the Pacific Ocean.
But it’s certain to be made worse by climate change. Professor Michael E. Mann from the University of Pennsylvania said on Twitter: “It’s the combined effect of both climate change and El Niño when it comes to wacky weather. Right now it’s a tag team effort, and we can expect some really extreme and potentially dangerous persistent weather extremes this summer.”
Dr Matt Palmer from the Met Office told FactCheck that the marine heatwave has slightly cooled in the past few days, but is ongoing and may pick up again in the coming weeks.
Dr Palmer said: “This event tells us that our climate is now in uncharted territory. Greenhouse gas emissions from human activities are warming the climate at a rate that is unprecedented in at least the last 2,000 years. We know that in our warming climate marine heatwaves will become more intense, of longer duration and greater extent.”
What it all means
Warmer oceans generally lead to more extreme hurricanes, as storms pick up energy via heat when they gather over the seas and then hit land with more intensity — lasting longer and causing more damage.
While El Niño emerges from warmer Pacific seas, in the Atlantic it can alter climate patterns which then lead to a dampening of hurricane conditions. So for the Atlantic hurricane season specifically, there may be two countervailing forces this year.
But the question for many has been whether these heating seas and climate trends outstrip what climate models have been predicting.
For example, one impact of hotter oceans is melting sea ice. This can raise sea levels and further increase global warming through the decrease in white ice which bounces away the sun’s rays.
In the Antarctic, recent sea ice levels have dropped to levels never seen before — both for total sea ice area and sea ice extent, a term used to describe the total area with at least 15 per cent of sea ice cover.SOURCE: NASA
In the Arctic the equivalent figures are low but not the lowest. But the European Space Agency said the current marine heatwave may just not have reached and impact ice in the Arctic yet.
For marine heatwaves, the impact on decreasing sea ice cover and decreased ability to absorb human-induced heating raises the question of passing tipping points — irreversible moments in climate change which spiral out of control.
The Met Office also told FactCheck that the recent events don’t suggest we’re at that point yet, but that the current trends suggest we’re traveling in the wrong direction.