Governments have produced a TL;DR version of a key report explaining the climate crisis. Stuff’s Olivia Wannan, Eloise Gibson and Kate Newton chart your way through the evidence.
Governments admit that, collectively, they are not doing enough to avoid the catastrophic effects of climate change – and time is running out.
The admission comes in a report out on Tuesday, informed by eight years of work by hundreds of climate scientists. This publication, the final out of four, required governments to confront the dire warnings of climate scientists.
Recent climate disasters increased the stakes, said University of Canterbury researcher Bronwyn Hayward – part of a team that spent the last “intense” week going over each line of the report with diplomats.
It was significant that government delegates agreed to strong wording saying that the world needs strong action this decade, Hayward stressed. To have a chance of staying inside 1.5C-2C, action is needed on both carbon dioxide and methane, she said – a conclusion that was discussed “intensely” because of greater focus on methane in the summary compared with previous reports.
“We cannot ensure that we can protect communities and our livelihoods once our temperatures start rising over 1.5C,” she added. “The actions we take now will affect current and future generations – but for thousands of years.”
One of the most important conclusions is that climate change is here: the world has already heated by roughly 1.1C.
This ain’t computer modelling, this is what temperature records actually show (and it’s the fastest temperature change we’ve seen since human civilisation began).
The proof – summarised in the Intergovernmental Panel on Climate Change synthesis report – comes from far and wide:
Thermometers. Across the world, thousands of weather stations record temperatures. This data is supported by an array of satellites, tracking the amount of heat radiating from the planet’s surface at different points as they orbit. Land surface temperature measurements zoom up and down every day and rise and fall across the seasons. But when you step back from these zigzags, a clear trend emerges: the world is more than 1C warmer than it was in the pre-fossil-fuel era.
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Some bad stuff is happening.
Polar sea ice and ice sheets. At both poles, sea ice expands in the cooler months and contracts over summer. Antarctica’s ice is typically tracked by satellites, which photograph and collect microwave radiation to determine how much of the pole is covered.
In the north, scientists also make hands-on measurements. Submarines travelling under Arctic sea ice send out sonar beams and determine how thick the ice is – and thanks to the Cold War, scientists can access decades of data. Consistent with a warming planet, sea ice is comparatively scarce in recent years.
The Antarctic and Greenland ice sheets sit on top of land, and can be so massive they affect the earth’s gravitational field. For the last 20 years, satellites have tracked minor changes in the gravity of the sheets as sections have melted.
The gap between the last spring and the first autumn frost. Meteorology records show it’s increasingly rare to experience the iced blades of grass and frozen puddles of a 0C morning.
The dates when nature responds to spring. Spring flowers blooming at an earlier date would provide evidence of a warming climate with a shortening winter. That’s exactly what scientists discovered, when they compared 1200 years of records on Kyoto’s cherry blossoms. Recently, the trees are flowering over a week earlier than normal.
Horticulture crops are responding similarly: budding sooner and losing their autumn leaves later. According to UK historical records, migrating birds on their spring journeys are also sighted earlier in the year.
The height of the sea. Water expands as it heats, pushing up the surface of the sea. That’s compounded by glacier and polar melting. Scientists have measured these effects using coastal yardsticks and satellites that send a radar pulse down to the surface of the Earth – most often, ocean rather than land – and record when it bounces back.
As with temperatures, the height of the sea naturally varies each day. But when you look at the data over decades, the short-term variability falls away and a trend emerges: globally, the ocean has risen 14cm over the past 70 years – and the phenomenon is accelerating.
How do we know it’s our fault?
Logic points us towards human culpability.
A basic science experiment shows that burning fossil fuels releases the greenhouse gas carbon dioxide. In the atmosphere, these create a blanket of heat around the planet (just ask Venus, which despite being further from the sun, is hotter than Mercury thanks to these gases).
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The scientists aren’t relying on logic alone but cold, hard data.
The rise in the concentration of carbon dioxide in the atmosphere is regularly measured across the world, said Victoria University climate scientist James Renwick. “When you do the sums on how much oil and coal gets burned every year, that works out to be how much carbon dioxide we measure.”
Next, oxygen is falling accordingly, Renwick said. “That’s a sure sign of burning. You use oxygen to produce carbon dioxide.”
Finally, when scientists focus on the carbon part of the carbon dioxide molecule, the atom has a chemical signature that indicates it’s been underground for a long time.
While natural causes could be to blame, the evidence suggests these are having a minimal impact.
The sun could, in theory, be sending more energy towards us – but our very many instruments aren’t picking up a significant increase in sunlight. If there was extra light, it would warm the outer layers of the atmosphere first, Renwick said, and this area is actually cooling.
Volcanoes can release carbon dioxide, he said. But seismic activity is well monitored, and there’s been no rapid increase.
“We may not know the location of every volcano under the ocean on the planet, but we know where most of them are – and that volcanic activity is not changing.”
Overall, scientists and governments in today’s report conclude global temperatures rose 1.09C by the end of 2020. Humanity is responsible for 1.07C.
How hot from here?
The IPCC report warns rapid action is needed to limiting warming to 1.5C, a comparatively safe scenario. Above this temperature, the Greenland ice sheet could collapse – raising the oceans by 7 metres and threatening Pacific nations. Coral reefs are likely to become a memory.
The world can’t wake up one morning and go cold turkey on fossil fuels. Every new fossil-fuelled power plant, heater and car locks a lifetime of carbon pollution.
If the world is serious about limiting warming to 1.5C – and governments promised they were by signing the Paris Agreement – we’ll need to stop creating this fossil-fuel-guzzling infrastructure as soon as possible and retire much of the existing stuff before it reaches the end of its life.
Kate Newton/Stuff
Existing things will create twice as much carbon as the world can emit for a decent shot at 1.5C.
The world has dragged its feet for so long that 1.5C is tough to achieve without vacuuming up and permanently storing carbon dioxide. This tech is still young, but deployed at scale could allow the world to briefly “overshoot” 1.5C but remove enough greenhouse gas to later settle at the target.
Even so, we’re far from that scenario. The world’s current trajectory will cause 2.8C of warming before the end of the century, the report concluded.
Since climate impacts get progressively worse, that path leaves children and the next generations to a rough future, Hayward said. “We struggle, as scientists, to get the language right on how serious this is.”
A bright spark in the report is that it’s never been cheaper to switch to green energy. In many cases, new renewable energy is even cheaper than maintaining old fossil-fuelled power stations.
The world has the solutions, Hayward said. “We just need the political will.”
These can be implemented poorly, without the voices of local and Indigenous communities, or well.
The report demonstrates global action is falling far behind the pledges made. More than 70 countries – including the world’s biggest polluters such as China, the US, the EU and India – have set a date for net-zero.
By law, Aotearoa needs to achieve net-zero by 2050.
After this point, the country will need to absorb more emissions than are created.
While governments are passing green laws, this isn’t at the pace required to achieve these targets. Last year, the IPCC projected that under governments’ existing policies, emissions would rise in coming decades.
Diplomats will re-confront this shortfall later in the year. At the next UN climate conference, governments’ progress (or lack of) will be added up during a “global stocktake”.
To limit the damage to 1.5C or even 2C, carbon dioxide and (importantly for New Zealand) methane need to start falling right away. Yet there is still hope, even for 1.5C – the point of no return hasn’t been passed yet.
In good news: people will experience a near-immediate boost to their health when fossil fuels use falls, as air pollution clears.
Across the globe, 18 countries have managed to reduce their emissions for at least a decade. New Zealand is not one of them, Hayward stressed. Although we are small, “three quarters of the world is small,” she said.
“We are quite a significant outlier now, in the way in which our emissions are continuing to rise.”
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