The TLDR: Let’s be honest. Isn’t that how we feel when scientists put out a climate change prediction—full of doom and gloom, leaving us feeling powerless and anxious? That said, the latest UN Assessment Report is important because it is based on the best available evidence. It gives us a clear picture of where we are, where we are headed—and how to change course. And we keep it focused so you don’t have to wade through monotonous prophecies of catastrophe.

Researched by: Sara Varghese and Panu Hejmadi

Why this report matters

Every 6-7 years, hundreds of scientists from around the world put out an Assessment Report commissioned by the United Nations Intergovernmental Panel on Climate Change (IPCC). Authored by 234 experts from 66 countries, this one is the sixth since 1988—and has been eight years in the making. It is the most comprehensive and based on the best available data contained in 14,000 studies. So it is also the most precise: “It represents the world’s full knowledge to date of the physical basis of climate change.”

Also this: What is striking is the level of certainty—since scientists tend to hedge their bets in most such reports. As the BBC News notes:

“It is the confidence of the assertions that the scientists are now making that is the real strength of this new publication. The phrase ‘very likely’ appears 42 times in the 40-odd pages of the Summary for Policymakers. In scientific terms, that's 90-100% certain that something is real.”

Big point #1: Humans are guilty as charged

Previous such reports have posited a strong link between human activity and climate change. This IPCC report says the connection is “unequivocal and indisputable.” As one expert notes, it’s the “strongest statement the IPCC has ever made.” The Guardian’s graph below charting rising temperatures since 1850 lays this out fairly clearly. Note the steep upward spike since 2000.

Also important to note: Many changes triggered by warming temperatures are irreversible, and already here. And this is where we are:

• The average global temperature has risen by 1.09°C in the decade between 2011-2020—compared to pre-industrial levels (1850-1900). The target of the Paris Climate Accords is to limit that increase to 1.5°C—or at worst, to 2°C.
• The last decade has possibly been the hottest the planet has been in 125,000 years.
• Glaciers are melting at a rate “unprecedented in at least the last 2,000 years.”
• Levels of carbon dioxide in the atmosphere have not been this high in at least 2 million years.
• The recent rate of sea level rise has almost tripled compared to the period 1901-1971.
• Ocean levels have risen eight inches on average over the past century, and the rate of increase has doubled since 2006.

The big ‘but’: If we act now, we can avert the most harrowing future, and keep the temperature rise to just at 1.5°C.

Big point #2: It’s getting hotter, faster

Until now, experts projected that we will hit the 1.5°C threshold around 2050 or beyond. The report predicts we will hit it between 2030-2035—which is in our lifetime. Even with our best efforts, we will exceed the 1.5°C threshold for some period of time—before temperatures come down and stabilise at that threshold. 

The report lays out five different scenarios—based on how much we reduce greenhouse gas emissions. In the most optimistic scenario, we hit net zero around 2050. In the worst case, we double our emissions that same year. The world will look something like this based at what temperature threshold we hit:

Where we are: At current levels of emissions, we are headed toward a rise of 3°C.

Graphic to note: This is what the world would look like at various temperatures—with the darkest red indicating a rise of 7°C or more:

Big point #3: Rise in sea levels is irreversible

Irrespective of what we do, sea levels will rise 15-30 cm (6-12 inches) by the middle of this century: 

“Under the very low emissions scenario, the report estimates that global mean sea level rise could be between about one to two feet by the year 2100. But in a very high emissions scenario, that figure would be six and a half feet, and over 16 feet by 2150.”

One of the authors says: “That is just scary, because it's maybe not at the end of our lifetime, but it is around the corner and it will be committing this planet to a big legacy.” Here are the different levels of sea rise as per the five scenarios:

Big point #4: Extreme weather will become routine

When we throw around numbers like 1.5°C or 2°C, we are talking about the average temperature of the planet. The reality is that even at 1.5°C, we will experience frequent stretches of more extreme weather, experts point out:

“The increases in temperature, rainfall, or other factors like glacier melting that are reported in the assessment (report), are mainly averages. But averages often mask the extremes. In a 2°C warmer world, for example, not every day would be 2°C warmer than pre-industrial times. Some days can be 6°C to 8°C, or even 10°C, warmer. That is how global warming will manifest at the local levels.” 

Also this: 

“Consider a dangerous heat wave that, in the past, would have occurred just once in a given region every 50 years. Today, a similar heat wave can be expected every 10 years, on average. At 1.5°C of global warming, those heat waves will strike every 5 years and be significantly hotter. At 4 degrees of warming, they will occur nearly annually.”

The same goes for floods, droughts and other ‘natural’ calamities. 

Big point to note: An increase of even half a degree will have a significant impact! As one lead author of the report puts it: 

“With every additional amount of global warming, we will see greater changes in the climate. Every additional half degree of warming will cause [an] increase in the intensity and frequency of hot extremes, heavy precipitation and drought. At 2 degrees of global warming, heat extremes would more often reach critical tolerance thresholds for agriculture and human health. At a global scale, extreme daily rainfall events would intensify by about 7% for each additional °C of global warming.”

Is there any good news?

One: We can get a speedy handle on the problem by drastically cutting down our methane emissions. It has 80 times the global warming power of CO2—but we can get rid of it quickly:

“It's a very powerful lever we have to affect short-term climate change. Because once you emit a ton of CO2 in the atmosphere, it stays there for a very long time—at least a good part of it. But if you put a ton of methane in the atmosphere, it's pretty much all gone after 10 years, 12 years, or so. And so that means if you were to cut methane emissions, the amount of methane in the atmosphere falls almost immediately.”

Two: We can still save the 1.5°C target—even if we have very little time to do it:

“Doing so would require a coordinated effort among countries to stop adding carbon dioxide to the atmosphere by around 2050, which would entail a rapid shift away from fossil fuels starting immediately, as well as potentially removing vast amounts of carbon from the air. If that happened, global warming would likely halt and level off at around 1.5°C.”

Three: We will get an opportunity to act quickly at the upcoming UN climate change conference known as Cop26—where 197 countries will meet in Glasgow this November. Each country is expected to come armed with a plan to reduce greenhouse gas emissions. And the hope is the IPCC report will act as a reality check—and spur some much-needed urgency. 

The bottomline: is best summed up by the UN Secretary General António Guterres, who warned: “[This report] is a code red for humanity. The alarm bells are deafening, and the evidence is irrefutable.”

Reading list

BBC News has a quick recap with five big takeaways from the report. Wired magazine digs into the data. The Guardian looks at the likely response from key governments. Mongabay looks at its implications for India. This interactive atlas shows how different countries will be impacted as global temperatures rise. Nature smacks down the IPCC for unreadable reports full of jargon. Read the original report here, and the highlights here.