New Scientist – August 17, 2019

17 August 2019 | New Scientist | 15

Astronomy

Leah Crane

HUGE blobs of hot plasma have

been spotted hurtling through the

sun’s chromosphere – the area

between its surface and its outer

atmosphere. They could help

explain how the sun’s atmosphere

gets so hot.

Shuhong Yang at the National

Astronomical Observatories of the

Chinese Academy of Sciences and

his colleagues spotted what they

called “chromospheric cannonballs”

in a series of observations using

the New Vacuum Solar Telescope

in China in 2017 and 2018.

On average, these projectiles are

about 1.5 billion cubic kilometres in

size, and they have an average mass

of about 150 million kilograms

(The Astrophysical Journal Letters,

doi.org/c88v). They race across

the sun at an average speed of

56 kilometres per second.

“If you were watching from near

the sun, it would look like a huge,

fast-moving ball-shaped monster

flying along a curved trajectory,”

says Yang. The trajectories appear

to follow the sun’s magnetic field in

an arc, like the path of a cannonball

flying through the air. Yang and his

team say that these scorching blobs

may be propelled by a process called

magnetic reconnection, in which

parts of the sun’s magnetic field

crack open and then snap back

together, releasing a burst of energy

that can toss plasma across the sun.

It isn’t yet clear whether these

blobs can be attributed to magnetic

reconnection, says Marco Velli

at the University of California,

Los Angeles. If they can, observing

them might be key to understanding

why the sun’s atmosphere – its

corona – is so much hotter than

its surface, he says. ❚

Great balls of fire

spotted flying

around the sun

“It would look like a huge,
fast-moving ball-shaped
monster flying along
a curved trajectory”

NEARLY every plan for

preventing Earth from warming

by dangerous amounts relies in

part on generating energy by

burning crops. But this may not

be the panacea many had hoped

for: a special report from the

Intergovernmental Panel on

Climate Change (IPCC) on global

warming and land use says this

“bioenergy” would reduce

biodiversity and push up food

prices. Fortunately, it has some

alternative solutions.

Why is the IPCC looking at how

we use land?

Land is a major source of

greenhouse gas emissions

but it also soaks up a lot of the

extra carbon dioxide we are

pumping into the atmosphere.

A quarter of all anthropogenic

greenhouse gas emissions so

far are a result of the ways we

exploit land, and the global food

system produces a third of all

emissions. We need to use land

in sustainable ways that soak

up CO 2 rather than releasing it.

This report is about more than

just climate change then?

Yes. The full title is: “Special

report on climate change,

desertification, land

degradation, sustainable land

management, food security,

and greenhouse gas fluxes in

terrestrial ecosystems”. Phew!

How does bioenergy help us?

The idea is to grow plants

such as fast-growing grasses,

burn them in power plants to

produce electricity, and then

remove and store the emitted

CO 2 rather than letting it go out

the chimneys. The grasses suck

in CO 2 as they grow, helping to

remove it from the atmosphere.

Sounds great, what’s the

problem?

Environmentalists have been

saying for years that relying on

bioenergy to remove CO 2 would

be a disaster. Now it’s finally

official. The report found that,

if we don’t slash fossil fuel

emissions, we would need

stupendous amounts of land

to remove enough CO 2 to limit

warming to 1.5°C above pre-

industrial levels in this way.

Using all this land for bioenergy

could lead to side effects like

desertification.

What about food security?

Food prices are projected to

rise anyway as global warming

affects food production. If we

employed large scale bioenergy,

it would compete with food

production and push up food

prices even further.

Does this mean we can’t use

land to help capture carbon?

Far from it. Recently the land

has been soaking up far more

CO 2 than it is releasing.

Deforestation released

6 gigatonnes of CO 2 between

2008 and 2017, but plant growth

soaked up 12 Gt of CO 2. There are

many ways we can make it soak

up even more, such as restoring

natural forests.

It’s not all doom and gloom then?

Definitely not. Many ways

of reducing emissions and

adapting to a warmer world

actually benefit people and

the environment.

Can you give an example?

If people cook with electricity

from wind or solar instead

of burning firewood, it helps

prevent desertification,

improves health and reduces

emissions all at once. The

report also says “genetic

improvement” of plants and

livestock will help. Many will

read that as meaning genetic

engineering.

What about eating less meat?

The report doesn’t say eating

less meat will reduce emissions

in as many words, but that’s

certainly the implication. It says

balanced diets, featuring plant-

based and animal-sourced food

produced in sustainable and

low-emission systems “present

major opportunities”. ❚

Briefing IPCC land use report

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Using land to save the climate

A UN report says we drastically need to rethink our land

use to limit global warming, finds Michael Le Page

How we use land will affect

how well we can tackle

climate change