The state of the climate in 2023
Editor/Mohamed Shihab
In the last few years, the world has experienced extreme weather, record temperatures and rapid ice melt. Where are we on key climate indicators?
This week the UN's climate science body is releasing a major report on the climate changes happening worldwide due to human activity.In its last report in 2021, the Intergovernmental Panel on Climate Change (IPCC) warned that human activity is changing the climate in unprecedented and sometimes irreversible ways. Scientists said that drastic emissions reductions were needed this decade to keep global warming below 1.5C and protect the world's most vulnerable ecosystems and communities.
This latest report is likely to "emphasise that time is running out for the easier solutions and the more gradual transitions to a carbon free economy", says Bonnie Waring, senior lecturer at the Grantham Institute for climate change and the environment at Imperial College London.
In the last few years, the world has experienced devastating extreme weather caused by climate change, record temperatures and rapid ice melt. Scientists are now tracking the state of the climate more than ever. Here are five key indicators to assess its health in 2023.
Atmospheric CO2 levels
The amount of CO2 in the atmosphere this year is forecast to be 419.2 parts per million (ppm), according to the Mauna Loa observatory in Hawaii. The global average last year was 417.2ppm.
In the past 50 years, we have added 100ppm of CO2 to the atmosphere, according to Martin Siegert, co-director of the Grantham Institute. "It's going up about two points every year, so in 100 years we'd end up at 600ppm and that would be just crazy," he says.
The last time CO2 levels exceeded 400ppm was around four million years ago, during the Pliocene era, when global temperatures were 2-4C (3.6-7.2F) warmer and sea levels were 10-25m (33-82ft) higher than today.
"Atmospheric CO2 levels continue to rise. This is a major issue because we are getting dangerously close to a future where we will not be able to keep [global] warming below 1.5C," says Waring.
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Last year the IPCC warned that removing CO2 from the atmosphere is essential because even big emissions' cuts won't be enough to limit global warming. "That puts us in a very dangerous situation, because we have very few scaleable strategies for doing this," says Waring. Technologies to capture and store CO2 are still emerging, very expensive and as yet unproven. (Read more about the plans to pull CO2 from the air).
"It's an absolute, worst-case scenario that we need to do this, because other things have failed," says Siegert, adding that there is not one "silver bullet" to tackling climate change. "We can't put it all on carbon capture."
Forest loss
Planting more trees and protecting carbon-absorbing ecosystems is one of the most effective ways of scaling up carbon capture. But forests worldwide are shrinking at an alarming rate. According to new research, destruction of tropical forests is far outstripping the current rate of regrowth.
This is affecting how much carbon tropical forests retain. The loss of forest carbon in the tropics was twice as high in 2015-2019 as it was in 2001-2005, according to a 2022 study.
One of the biggest concerns is that over a quarter of the Amazon rainforest now emits more carbon than it absorbs as a result of deforestation and dryer conditions. "We will not only lose this spectacular biodiversity that's associated with that ecosystem, but there will be less carbon stored on land going back into the atmosphere," says Waring. "This is a tipping point where we see a different kind of ecosystem in the Amazon basin that is becoming more like a savannah than a rainforest and [it is one] we're extremely worried about."
Record heat
2022 was the sixth-warmest year since records began in 1880. The oceans were the hottest ever recorded in 2022. The 10 warmest years on record have all occurred since 2010.A total of 28 countries experienced their warmest year on record in 2022, including the UK, China and New Zealand.
Record temperatures usually coincide with an El Niño event (a large band of warm water that forms in the Pacific Ocean every few years), but last year was a La Niña event (the opposite of El Niño when a cooler band of water forms). Without La Niña lowering temperatures, 2022 would have been much hotter.
"You don't need the hottest year globally ever to experience the hottest weather [in some places]," says Siegert, pointing to record heatwaves in countries such as Europe, India and China. According to scientists from World Weather Attribution, an independent research institute, climate change played a clear role in increasing the likelihood of all these events.
Melting ice
Arctic sea ice has shrunk to its fifth-lowest maximum on record, retreating to 14.62 million sq km (5.64 million sq miles)."Overall, we have thinner ice than we used to have…that leads to overall less ice at the end of summer," says Julienne Stroeve, a polar scientist from University College London.
The rapid loss of Arctic sea ice is not just a symptom of climate change, but also a driver. It is diminishing the albedo effect, which is the capacity of the snow and ice to reflect heat. "It's a runaway feedback process," says Siegert. "As the ice starts to retreat, the white reflective surface is replaced by a dark heat-absorbing surface, which leads to further loss of sea ice."There is now less sea ice surrounding Antarctica than at any time since satellites started measuring it in the late 1970s.
The US National Snow and Ice Data Center said that stronger-than-average winds combined with warmer ocean and air temperatures reduced coverage to just 1.91 million sq km (737,000 sq miles) on 13 February.This was a new record low and only the second year that Antarctic sea ice coverage fell below two million sq km (772,000 sq miles). The previous record-breaking minimum of 1.92 million sq km (741,000 sq miles) was reached on 25 February last year.But it's the melting of Antarctica's ice sheets that is the real concern because it could lead to a dangerous rise in sea levels, says Siegert.
Antarctica is losing ice mass at a rate of 150 billion tonnes a year. The East Antarctic ice sheet could lead to an estimated 52m (170ft) of potential sea level rise, compared to the West Antarctic ice sheet which could result in 3-4m (10-13ft). (Read more about why East Antarctica is a "sleeping giant" of sea level rise).
"For the last few thousand years, it's always been the temperature of the ocean [which leads water to expand] that led to centimetres of sea level rise. But now it's the ice sheets and they don't talk in centimetres, they talk in metres," says Siegert.
Thawing permafrost
Across the northern hemisphere, permafrost – the ground that remains frozen year-round for two or more years – is also warming rapidly."From the observational networks we see clear warming of the permafrost areas," says Stroeve. This is concerning because permafrost contains a huge amount of greenhouse gases, including CO2 and methane, which are released into the atmosphere as it thaws.
"Since it is estimated that the current carbon storage in permafrost is more than twice [the amount] in our atmosphere, this is concerning as it will enhance overall global warming," says Stroeve.
Soils in the permafrost region, which spans 23 million sq km (8.9 million sq miles) across Siberia, Greenland, Canada and the Arctic, hold almost 1,700 billion tonnes of carbon.
Thawing permafrost can also damage existing infrastructure and impact the livelihoods of indigenous communities, who rely on the frozen ground to travel and hunt on the edge of the sea ice. (Read more about the Inuit knowledge vanishing with the ice).
The current state of the climate highlights "why it's so important that we take this seriously now", says Siegert. "We can do something about climate change now and recognise that, if we don't, things will get worse for people who come after us."
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