Climate change: Lockdown has 'negligible' effect
on temperatures
By Matt
McGrath
Environment
correspondent
7 August
2020
The global
restrictions saw roads and motorways hardly used for several months
The
dramatic drop in greenhouse gases and air pollutants seen during the global
lockdown will have little impact on our warming planet say scientists.
Their new
analysis suggests that by 2030, global temperatures will only be 0.01C lower
than expected.
But the
authors stress that the nature of the recovery could significantly alter the
longer term outlook.
A strong
green stimulus could keep the world from exceeding 1.5C of warming by the
middle of this century.
Previous
studies have already established that there were significant changes to
greenhouse gas emissions as transport systems shut down around the world in
response to the pandemic.
Global
daily emissions of CO2 fell by 17% at the peak of the crisis.
The new
study builds on these findings by using global mobility data from Google and
Apple.
Prof Piers
Forster from the University of Leeds, who led the study, worked with his
daughter Harriet on the research, when her A-Level exams were cancelled.
With other
researchers, they calculated how 10 different greenhouse gases and air
pollutants changed between February and June 2020 in 123 countries.
They found
that the drop off peaked in April, with CO2, nitrogen oxides and other
emissions falling between 10-30% globally, mainly due to declines in surface
transport.
But this
new work shows that some of the declines in greenhouse gases actually cancelled
each other out in terms of warming.
Nitrogen
oxides from transport normally have a warming impact in the atmosphere.
While they
went down by 30%, they were matched by a drop in sulphur dioxide, which mainly
comes from the burning of coal.
Emissions
of this gas help aerosols to form, which reflect sunlight back into space and
cool the planet.
This
balancing out, combined with the temporary nature of the pandemic restrictions,
mean the impact on warming by 2030 will hardly be felt.
"Although
temporary changes can help, you need to reduce CO2 permanently to make a dent
in global warming," said Prof Piers Forster from the University of Leeds.
"CO2
is long lived in the atmosphere, so you effectively need to reduce emissions to
zero for a long-time before you begin to cancel out the effects from decades of
past emissions."
Harriet
Forster, who co-authored the paper with her father, said that while the recent
impacts won't last, there is a golden opportunity for governments to change
course.
"Our
paper shows that the actual effect of lockdown on the climate is small. The
important thing to recognise is that we've been given a massive opportunity to
boost the economy by investing in green industries - and this can make a huge
difference to our future climate," she explained.
Right now,
road traffic is still down in many countries say the authors, with the Google
data showing all modes of UK transport still 25% or so down, while the official
UK government data has cars still 12% down, but with buses and trains running
at less than 50%.
The
research team says that if transport goes back to what it was, and the world
strongly invests in fossil fuels during the recovery, there is a very high
probability that the world will go above the 1.5C warming threshold by 2050.
But if the
recovery is strongly green, avoids fossil fuel lock-ins and bail outs, and cuts
global emissions to net zero by 2050, the world would have around a 55% chance
of staying under 1.5C by the middle of the century.
So what
needs to be done to help that happen? Study co-author Prof Corinne Le Quéré
from the University of East Anglia says there are a number of steps that should
now be taken.
"In
cities, it is to support cycling and walking (including electric bikes) because
this has multiple benefits for climate, for reducing air pollution, and for
health," she told BBC News.
"Encouraging
remote working until social distancing measures are lifted releases the
pressure on public transport, which can continue to be used. As soon as
possible all cars will need to be electric."
"The
economic stimulus post-Covid could greatly help support that change in the car
manufacturing industry towards the production of electric cars alone."
Prof
Forster is optimistic that the challenge can be met.
"Disasters
are often historically the time of biggest change," he said.
"For
once government, industry and public voices are all pretty aligned that green
jobs and green investments are the way to build back better."
"We
just need to do it."
The study
has been published in the journal Nature Climate Change.
Sem comentários:
Enviar um comentário