Misleading posts about how CO2 affects the Earth

Carbon dioxide (CO2) contributes to global warming, but social media posts claim that an image showing an increase in vegetation over time suggests the greenhouse gas is actually good for the planet. This is misleading; the map is more than five years old, research shows the “greening” trend may be ending, and experts say rising temperatures can harm plants.

“Look closely. The effects of CO2 on the planet…” says a November 27, 2022 tweet by former University of Toronto professor Jordan Peterson that has tens of thousands of interactions.

Screenshot of a tweet dated December 13, 2022

Similar claims have been circulating on Twitter and TikTok.

The posts spread as scientists warned at the United Nations COP27 climate summit in Egypt that global emissions of CO2, a major driver of climate change, will hit record highs in 2022.

Increased CO2 is associated with warmer temperatures and research suggests it could increase the risk of extreme weather events. Most scientists agree that recent climate change is due to greenhouse gas emissions related to human activity.

Increased CO2 may also benefit plant growth, but to say it’s good for the planet is misleading.

Green effect

A reverse image search reveals that the map shared online comes from a 2016 study published in Nature Climate Change by an international team of scientists. They used satellite data to see how leaf area index (places on Earth that display green leaves) evolved from 1982 to 2015.

“As much as half of all vegetated land is greener today, and surprisingly, only 4 percent of the land has become browner,” said Pep Canadell and Yingping Wang in an April 25, 2016 article by The Conversation on the results of the study.

The co-authors argued that the Earth is greener primarily because increasing CO2 concentration in the atmosphere has a fertilising effect, but noted that this should diminish over time as plants face nutrient limitations in a warming world. .

Canadell and Wang also stated, “It is clear that the benefits of a greener Earth far outweigh the estimated negative impacts of extreme weather events (such as droughts, heat waves and floods), sea level rise and ocean acidification.” . “

Other experts have said that rising temperatures can have negative effects on vegetation and that higher atmospheric CO2 can alter the nutrient content of crops. Other studies have found that higher temperatures will negatively affect the crop yield of global diet staples such as wheat.

narrow interpretation

Ranga Myneni, a professor in Boston University’s Department of Earth and Environment, also worked on the 2016 study. He told AFP in a Dec. 13, 2022 email that focusing on a “short-term effect of higher growth of plants from a higher CO2 concentration misses the important point.”

“CO2 is a greenhouse gas, it is causing climate change whose effects include global warming, sea ice loss, sea level rise, etc,” Myneni said.

He added, “I’ve tried many times to put our findings into context, but some people are bent on interpreting our work narrowly.”

Myneni pointed to his most recent research published in Biogeosciences in 2021, which revealed “a slowdown in greening and a strengthening of browning trends, particularly over the past two decades.”

He also said that carbon emissions from human activities such as burning of fossil fuels and deforestation are responsible for increasing the concentration of CO2 in the atmosphere, a fact confirmed by the latest report of the International Intergovernmental Panel on Climate Change report.

“There is no benefit to the high concentration of CO2 in the atmosphere,” Myneni said.

AFP has verified here other false and misleading claims about climate change.

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