418.08 ppm: tracking regular climate news

Welcome to our regular segment on new climate news stories you might have missed. The title refers to the daily average global concentration of carbon dioxide within the Earth’s atmosphere in parts per million (ppm). Meaning that for every million air particles, currently about 418.08 of them are CO₂.

Black Summer bushfires changed the chemistry of our atmosphere

The Black Summer bushfires of 2019-2020 had a dramatic effect on the chemistry of our upper atmosphere and may destroy ozone, according to a study by US and Canadian researchers.

The study, which is published in Science, finds “unexpected and extreme perturbations in stratospheric gases beyond any seen in the previous 15 years of measurements”.

The researchers used satellite data to make these observations. The stratospheric gases they found include formaldehyde, chlorine nitrate, chlorine monoxide, and hypochlorous acid.

Several of these chemicals could affect or destroy ozone.

The paper also reports a decrease in ozone, nitrogen dioxide, and hydrochloric acid in the stratosphere.

River carbon doesn’t always flow to the sea

What’s more complicated than modelling carbon storage or water movement? Modelling both at the same time! An international team of researchers has come up with a more detailed analysis of how carbon moves through streams, rivers, and oceans, finding that stored carbon doesn’t always end up where you think it is.

The researchers have published their description of land-to-ocean aquatic continuum, or LOAC, of carbon in Nature.

“The complexity of the LOAC, which includes rivers, groundwater, lakes, reservoirs, estuaries, tidal marshes, mangroves, seagrasses, and waters above continental shelves, has made it challenging to assess its influence on the global carbon cycle,” says co-author Professor Pierre Regnier, a researcher at the University of Brussels, Belgium.

Modellers often assume there’s a direct pipeline of carbon from rivers to oceans, and that most of the carbon carried there is natural. But this study found that the LOAC carries a substantial amount of anthropogenic carbon too. This means that the ocean probably absorbs more of our carbon, and the land less, than other models might suggest.

Quick methane action could save the Arctic

On current trajectories, the Arctic could be ice-free in summer by the end of the century. But with a sharp turnaround in methane emissions, things could remain icy until well past 2100, according to a paper in Environmental Research Letters.

Methane is a much more potent gas than carbon dioxide at absorbing heat, so reducing methane emissions can have a big impact. To date, little research focussing on the effects that methane mitigation specifically might have.

The paper finds that, if “all currently available solutions” for methane reductions were brought in, along with a reduction in CO₂ emissions, there’s an 80% chance the Arctic will still have permafrost by the end of the century.

“Reducing current methane emissions represents a huge opportunity to help pump the brakes on global warming,” says lead author Tianyi Sun, a researcher at the Environmental Defense Fund, US.

“Quickly cutting methane along with CO₂ is our best chance at preserving Arctic summer sea ice within our lifetimes and for future generations. We must do both.”

Maybe don’t suppress fires in savannahs

Bushfires and wildfires generally increase carbon emissions, since they’re literally burning carbon. This has led to proposals that we try to suppress natural fires, particularly in regions that burn every year or so like African savannahs, and plant more trees for carbon storage.

But a study published in Nature has called this into question, finding that the benefits of suppressing fires in a South African savannah led to only marginal increases in carbon storage.

The researchers examined 68 years of data from a long-term experiment in Kruger National Park, South Africa, where some plots are burned annually and others are burned every three years.

They found that the three-year plots improved carbon storage by 0.35 tonnes of carbon per hectare per year – almost 30 times lower than other estimates.

The researchers point out that, although burning does release carbon into the atmosphere, it also can help improve plant and soil carbon storage. They caution against fire suppression as a tool to lower carbon emissions.

Respite for Australia’s environment in 2021

Last year was a kinder one for Australia’s overall environment, according to a review by Australian National University researchers.

ANU researchers produce an annual Environment Report, which tracks everything from field measurements through to satellite data, and produces an overall score on Australia’s environmental condition.

After the devastation of the Black Summer bushfires in 2019-2020, the researchers found that 2021 was a much better year overall. The total environment score was 6.9 out of 10, compared to 2020’s score of 3.

While there have been some losses in biodiversity and an increase in emissions, the researchers say that dual La Niña summers have given the environment some time to recover with more rainfall, and fewer extreme temperature days.

“We’ve seen strong signs of recovery in all states and territories thanks to low fire activity, eased drought conditions and good rainfall which replenished parched soils, improved vegetation and led to better growing conditions,” says lead author of the report, Professor Albert van Dijk.

He points out, however, that this increased rainfall has now led to the devastating floods in Queensland and New South Wales – which fell outside the timeframe for this report.

Despite having fewer very hot days, 2021 was still the sixth warmest year on record.