Cold War nuke tests light up problem with present-day climate models

Sub: Sci

Sec: Nuclear energy

Context:

A study by an international team of researchers, recently published in the journal Science, suggests plants absorb more carbon dioxide from the atmosphere than expected and also store it for a shorter duration, before releasing it into their surroundings.

Findings

The researchers investigated the remains of nuclear bomb tests the U.S. and the Soviet Union conducted in the 1960s (cold war era) using climate models.
Relics of the Cold War: The explosions sprayed radioactive material around the planet, including a lot of it in the atmosphere.
One of them was carbon-14, an isotope also called radiocarbon.
- Its atom’s nucleus has two neutrons more than in the nucleus of the more common carbon-12.
- Radiocarbon is naturally found in minute quantities, but the nuclear bomb tests steadily deposited more and more of it in the atmosphere.
In 1963, Cold War powers signed the Limited Test Ban Treaty (LTBT) that prohibited nuclear testing over land, air, and under water.
The atmospheric radiocarbon concentration stopped increasing beyond this year.

How Radiocarbon affects plants?

Often, radiocarbon bonds with oxygen to form CO₂.
Plants, trees, and other vegetation absorb this CO₂during photosynthesis to produce food and, ultimately, energy.

Carbon stored in Plants

Plants absorb CO₂from the atmosphere during photosynthesis and use it to make glucose. A plant consumes some of the glucose, and some it stores as starch in its leaves.
In this process, some carbon is also lost when the plant exhales CO₂as it respirates.
Scientists don’t have a direct way to measure the rates at which vegetation loses and gains carbon. But they have been able to use satellite data to estimate how much carbon vegetation around the world hosts.
The researchers behind the new study used climate models to estimate the amount of carbon stored in vegetation around the planet in a year.
Previous studies had shown this value to be at least 43–76 billion tonnes of carbon per year worldwide.
But new study says it could be around 80 billion tonnes per year, with most of the carbon being stored in leaves and finer roots, i.e., the non-woody parts of the plant.

‘The whole system is cycling faster’

If the higher value of 80 billion tonnes per year is accurate, plants must also be shedding their carbon sooner than thought.
The whole system of carbon cycling faster than we thought before, says the team.

Radioactive representation

scientists say that radiocarbon needs to be better represented in climate predictions.