‘The scariest part of climate change is what we don’t know about it’

Humberto Barbosa, professor at the Institute of Atmospheric Sciences at Ufal (Federal University of Alagoas), was one of the Brazilian researchers who participated in the production of the UN (United Nations Organization) IPCC (Intergovernmental Panel on Climate Change) report. last day 9. “I was a reviewer for a panel working group,” he says.

Coordinator of the Laboratory for Analysis and Processing of Satellite Images at Ufal, Barbosa is one of the authorities when it comes to environmental and soil degradation in Brazil.

In an interview with UOL, he says that the water crisis that the country is facing this year — and that threatens to cause a new “blackout” — is already one of the fruits of climate change, especially a “collateral effect” of deforestation in the Amazon.

“The rainfall regime in the Southeast region of the country depends on evapotranspiration from the Amazon forest,” he says.

In 2019, Barbosa had already led chapter 4 of another IPCC report, which addressed the issue of land degradation—he signed the executive summary of the document. At that time, he already warned that the Southeast region would be the most affected by deforestation in the Amazon forest.

Despite the revelations already made by scientists in the new IPCC document, he says there is still much more to discover than what we already know about climate change.

It sounds like a cliché, but the scariest part of climate change is not what we know, but what we don’t know.

Read the interview below:

UOL – What are the points that you highlight in the new IPCC report?
Humberto Barbosa – The last comprehensive IPCC report was published in 2013, and in those eight years several important changes have taken place. I highlight the improvements in computational capacity and climate modeling; and advances at the frontier of knowledge about the Earth’s climate system, regional climate change and social vulnerability.

In this new document, scientists claim that the increase in pollution — caused by industrialization, urbanization, population growth and other forms of changes in land use and land cover — has made the planet warmer. Among the human causes that accelerate the process of climate change are: burning fossil fuels for energy generation, industrial activities and transport; change in land use; agriculture and livestock; solid waste disposal [lixo] and deforestation.

Humberto Barbosa - Disclosure - Disclosure

The researcher Humberto Barbosa

Image: Disclosure

In this context, can we fit in that climate change is responsible for the drought and the water crisis that the Southeast is facing?
The Earth’s climate is affected by many interacting systems, including food, energy and water production. Decisions in one industry have important effects in other industries. They also affect the physical systems of the atmosphere, land, ice and oceans. For example, consider how humans produce food. Farmers are limited by the climate in which they live, which provides certain ranges of temperature, precipitation and insolation.

Modern industrialized agriculture allows farmers to improve their local conditions by using fertilizers to increase soil nutrients or pumping water to irrigate crops. These strategies have tradeoffs: they increase food production, but they can also increase energy use or the conversion of undeveloped land to more agriculture—which potentially contributes to climate change. The increasing demands on Earth’s food, energy and water systems ultimately create higher risks regionally for everyone.

But is this related to the Southeast now? Was it something already expected, like an announced tragedy?
The peak of water consumption in São Paulo coincides with that of agriculture, which will require more and more irrigation. This tends to aggravate water use conflicts. And to top it off, climate change — especially where droughts and forest fires are becoming more frequent — can cause land degradation even in rich places like the state of São Paulo.

Does the Amazon then influence the entire system?
Yes, especially the Southeast region.

Why are we facing such a bad year? Is it routine?
The current year could still be wet and conditions improve, although the return of the La Niña phenomenon makes this less likely. Many IPCC researchers predict that deforestation is pushing the Amazon to a tipping point, beyond which it will gradually turn into a semi-arid savanna. If rainforest deforestation continues beyond a threshold of 20% to 25% of total deforestation, multiple cycles will trigger desertification in the Amazon basin.

Aug.16.2020 - Image shows fire in the region of Novo Progresso (PA), in the Amazon - Carl de Souza/AFP - Carl de Souza/AFP

Aug.16.2020 – Image shows fire in the region of Novo Progresso (PA), in the Amazon

Image: Carl de Souza/AFP

Will we live in a country, and a planet, with a different climate then?
We already live. Before 2005 we thought we understood the droughts in the Amazon. The dogma was as follows: droughts affected only a few areas, such as the relatively dry parts of the east and south of the basin, and only occurred during the El Niño years. But in 2005, we witnessed something that no one in living memory had ever seen before. Apparently, due to a combination of global warming and natural climate variability, the sea surface in the tropical Atlantic Ocean has become exceptionally warm.

Amazon experts scratched their heads and concluded that we had just witnessed a once-in-a-lifetime event—something we would never see again. And then, in 2010, it happened again. The second drought was even more widespread and devastating than the first.

This looks pretty serious…
Yes. Another potential source of unknown unknowns is environmental synergisms, which occur when two or more environmental threats amplify or operate together. It sounds like a cliché, but the scariest part of climate change is not what we know, but what we don’t know.

And these doubts, obviously, are also related to the Brazilian climate, right?
The magnitude of forest loss could lead the Amazon to such an inflection point that further jeopardizes the rain recycling process, which replenishes the Amazon’s water supply. A large increase in this pace of deforestation could cause climate change in both South and North America.

The IPCC predicts that precipitation will decrease in many areas of the Americas, including southeastern South America and the Mississippi River valley. [EUA]. The entire world would suffer from reduced agricultural production in these two regions, important global suppliers of agricultural commodities such as corn and soybeans.

In this case, the riskiest region in these changes would be the Southeast then?
Yes. The rainfall regime in the Southeast region of the country depends on evapotranspiration from the Amazon rainforest.

Should we prepare for water crises to become more common, as well as heavy rains?
The water cycle is intensifying as the climate warms — that means more intense storms, droughts and floods. The latest IPCC report warns that the water cycle has been intensifying and will continue as the planet warms.

Comparison shows impact of drought on Lago das Brisas (MG): the image on the left was taken on June 12, 2019 and the image on the right, on June 17 of this year - NASA - NASA

Comparison shows the impact of drought on Lago das Brisas (MG): the image on the left was taken on June 12, 2019 and the image on the right, on June 17 this year

Image: NASA

What does this mean in practice?
For example, the report documents an increase in both wet extremes, including heavier rainfall in most regions; and dry extremes, including drying in the Mediterranean, southwestern Australia, southwestern South America, South Africa, and western North America.

Quantitatively, globally, daily extreme precipitation events are likely to intensify by about 7% for every 1°C increase in global temperatures. This is the order of magnitude indicated in the report. The clearest effect of global warming is that a warmer atmosphere holds more water, leading to more extreme rainfall.

And why does the opposite occur too?
By the water cycle. The intensification of the water cycle means that wet and dry extremes and the general variability of the water cycle will increase, albeit not uniformly around the globe. That is, wet and dry extremes will continue to increase with future warming.

But are we already feeling the effects of this?
See, a rare warming of temperatures in the upper atmosphere, in the layer called the stratosphere, could modulate Brazil’s climate in the coming months. This warming started suddenly last week, in a phenomenon called “sudden stratospheric warming”. This could contribute with large volumes of rain in southern Brazil — mainly in Rio Grande do Sul — and below normal rainfall in central Brazil. The effects of stratospheric warming will start to be felt on the surface over Antarctica from the second half of October.

Knowing about these processes, both natural and man-made, can be crucially important for decision makers trying to manage risk.

So in short, we have to stop this climate change so we don’t have so much damage, right?
Yes. The scenario is still uncertain. That’s why, for example, we talk not just about the most likely outcomes, but also outcomes where the probability is low or still unknown but the potential impacts are large.

Previous events of stratospheric warming and associated wind shifts had their strongest effects in Australia in 2002 and 2009, where spring temperatures increased, rainfall decreased and heat waves and fire risk increased. In addition to warming the Antarctic region, the most notable effect will be a shift in the western winds of the Antarctic Ocean towards the equator.