The IPCC, the acronym in English for the Intergovernmental Panel on Climate Change, is immersed in the great review of the scientific literature on the climate crisis.
It is the sixth that has been carried out since this group linked to the United Nations was created in 1988 with the aim of laying the foundations of knowledge on global warming from the thousands and thousands of articles and research published on this subject.
The previous review was concluded in 2014 and served to adopt the Paris Agreement at the end of 2015. This review is serving to verify that the countries are not on track to comply with that pact, which seeks to make warming as less catastrophic as possible.
Also to certify that time is running out and drastic and urgent changes are needed.
The review consists of three blocks of documents and a final summary report.
In August 2021, the group I report was published, referring to the physical bases of climate change.
This February, the group II was published, which refers to the impacts and adaptation to warming.
And last Monday, group III was released, which focuses on mitigation, that is, on possible solutions.
The final synthesis report will be published in the autumn.
Hundreds of international scientists participate in this work, who must analyze tens of thousands of scientific articles and research.
After months of work, they produce a document of thousands of pages and a summary proposal of several dozen.
That summary is then reviewed point by point for two weeks by the team of scientists and by designated representatives of the nearly 200 countries participating in the UN climate negotiations.
These are some of the most relevant findings of this sixth review that serve to create a portrait of this global crisis.
Does climate change exist?
Yes. And it is the responsibility of only one of the species that inhabit the planet: the human being.
The first report of the three that have been published, the one released in August, struck down denialism from the front line by considering it "unequivocal" that the human being and his activities have "heated the atmosphere, the ocean and the land."
This has generated “widespread and rapid changes in the atmosphere, the ocean, the cryosphere and the biosphere”.
Since the first IPCC report, in 1990, the debate on the responsibility of the human being had gone through the conclusions of the experts until reaching this sixth review, when a paradigm shift occurred and there is no longer room for doubt: humanity She's the guilty.
Why is the human being responsible?
Behind this warming driven by human activities are greenhouse gases, which overheat the planet's surface.
Those gases—carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O)—have been present in the atmosphere for billions of years and are what help make the planet more habitable.
But the human being, mainly from the enormous increase in the burning of fossil fuels since the Industrial Revolution, has broken the existing balance and triggered its presence in the atmosphere.
For example, the concentration of CO₂ —the main greenhouse gas— is the highest that has been reached in the last two million years and those of CH₄ and N₂O had not reached such high levels in the last 800,000 years .
These gases stay in the atmosphere for decades or centuries, depending on the gas.
Carbon dioxide, the most abundant, can remain for centuries and methane disappears earlier, in one or two decades, although its heating power is much greater.
Due to past emissions, the rise in global temperatures—rising at a rate unprecedented in at least the last 2,000 years—cannot be stopped now and will continue until at least 2050.
How much has the planet already warmed?
The point taken as a reference is the average temperature of the period between 1850 and 1900. And in the last decade, 2011-2020, the global temperature of the planet's surface was already almost 1.1 degrees Celsius higher compared to those pre-industrial levels.
The warming of the land surface (1.6 degrees) is much greater than that of the ocean (0.9).
And there are some areas of the planet, such as the Arctic or the Mediterranean region, where the increase in temperature is much more pronounced.
If emissions continue at the same rate as up to now, average warming will reach 4.4 degrees by the end of the century, which will have much more disastrous consequences.
The last time the planetary surface temperature was 2.5 degrees above pre-industrial levels was three million years ago, when humans did not even exist.
Projection of the increase in average temperatures on the planet with a global warming of 1.5 degrees (top) and a warming of 4 degrees (bottom). IPCC Atlas
What limit should not be exceeded?
The Paris Agreement established that the countries of the world should reduce their emissions to ensure that the increase in temperature remains below two degrees at the end of the century and, as far as possible, below 1.5.
Is there still time?
This sixth revision has an ultimatum aftertaste, because the window of opportunity is closing while emissions continue to grow year after year.
The IPCC recognizes that in all emission evolution scenarios it is expected that the 1.5 degree barrier will be overcome in the next 20 years.
In the most optimistic scenario, with the climate plans of the most robust and rapid countries, this overcoming would only be temporary and then it could come down from that barrier.
Yet country plans now on the table under the Paris Agreement will see global emissions continue to grow until at least 2030. And, according to scientists' calculations, that will lead to 2% warming. 8 degrees.
What is there to do?
To achieve the goals of the Paris Agreement, “deep and, in most cases, immediate” reductions in emissions in the sectors are needed.
The IPCC traces possible trajectories to meet the goals of 1.5 and 2 degrees, and in all of them, global emissions have to peak before 2025. What happens next is what differentiates one from the other.
To stay below 2 degrees, emissions in 2030 must be 27% lower and 63% in 2050, taking those of 2019 as a reference. If you want to meet 1.5 degrees, that reduction must be 43% in 2030 and 84% in 2050. But, given the prospect of exceeding 1.5 degrees in a short period of time, a third scenario is proposed: that this exceedance is only temporary and the temperature then drops thanks to the measures put in place.
But not all countries emit the same thing - the richest are historically responsible for the problem - and not all sectors are equally important in this fight: only electricity, industry and transport accumulate 73% of all the emissions generated the human being
Or put another way, the fossil fuels that feed these three sectors are the number one responsible for climate change.
That is why the IPCC establishes specific reduction routes: to meet the goal of 1.5 degrees, in 2050 the global use of coal, oil and gas will have to have been reduced by 100%, 60% and 70%, respectively, compared to 2019. The reports contemplate that these reductions will be smoother if carbon dioxide capture and storage techniques are applied,
The clearest alternatives to fossil fuels are renewable energies, whose costs have plummeted in the last decade.
They are joined by energy efficiency, storage systems, smart grids, sustainable biofuels, hydrogen and the promotion of electric mobility.
But the IPCC also points to the need to rethink the way the world develops: "Current patterns of unsustainable development are increasing the exposure of ecosystems and people to climate hazards."
What has already caused the warming?
The IPCC confirms that "unprecedented" climate changes have already occurred in the last thousands of years and that in some cases they will be "irreversible" for centuries or millennia, such as melting ice and rising seas.
In addition, this sixth review recognizes that "the scope and magnitude of the impacts of climate change are greater than estimated in previous evaluations."
And it is considered "unequivocal" that "climate change is a threat to human well-being and planetary health."
One of the sections in which more progress has been made compared to the previous review is in the attribution of extreme weather events.
"Human-induced climate change is already affecting many extreme weather and climate events in all regions."
This translates to extreme heat waves having become “more frequent and intense over most terrestrial regions since the 1950s, while cold extremes (including cold waves) have become less frequent and less serious”.
It has also increased "the frequency and intensity of intense precipitation events."
What future awaits us?
Climate change cannot be reversed now and damage has already been done that will be irreversible.
But it is still up to humans to keep warming within safe limits if emissions are cut quickly, sustainably, and on a large scale.
If it is not done, the impacts will be worse.
For every half degree of warming, "clearly perceptible increases in the intensity and frequency of warm extremes, including heat waves and heavy precipitation events, as well as agricultural and ecological droughts, are caused."
Something similar occurs with damage to biodiversity.
Species losses due to climate change have already been detected.
And the forecasts are not good for the future: between 3% and 14% of the terrestrial ecosystem species that have been analyzed in this IPCC review cycle will be at a very high level of risk of extinction if warming reaches the 1.5 degrees.
If 3 degrees are reached, the risk will be multiplied by two.
And by 3.5 if the heating rises to 5 degrees.
Does this crisis affect everyone equally?
Climate change has already caused “widespread adverse impacts” on nature and people and its negative effects are felt “in all sectors and regions”.
However, the most vulnerable are hit much harder: between 3.3 and 3.6 billion people – close to half of the world's population – now live in contexts considered “highly vulnerable”, either because of their geographical location or because of their poor situation. socioeconomic, which makes them suffer more from the consequences of extreme weather events.
Or by the combination of both factors.
Global hotspots of high human vulnerability are in West, Central and East Africa, South Asia, Central and South America, Small Island Developing States and the Arctic.
And the consequence is devastating: "Between 2010 and 2020, human mortality from floods, droughts and storms was 15 times higher in highly vulnerable regions, compared to regions with very low vulnerability."
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