Latest COVID-19 science updates: coronavirus climate impact, dynamic lockdown and airborne droplets

Each week, Channel 4 News will provide a summary of key research papers, studies or developments from the world of COVID-19 science.

Study estimates daily carbon emissions fell by 17 percent on average during lockdown

A study has estimated that daily carbon emissions fell across the world by an average of 17 percent during the height of coronavirus lockdown.

The daily figures for carbon emissions seen during March and April when countries limited various activities to control the spread of the virus haven’t been seen since 2006, the study said.

Published on Tuesday in Nature Climate Change, the research was the first peer-reviewed estimation of the carbon impact of the global response to the coronavirus pandemic. It said that within the 17 percent average, some individual countries saw daily emissions drops of up to 26 percent at the lockdown peak .

Nearly half of the total global emissions reductions were from changes in surface transport like driving, the authors noted.

The annual emissions drop across 2020 was estimated to be around 8.6 percent compared to 2019. Previous estimates in recent weeks, for example by the International Energy Agency, put this figure between 5 and 8 percent.

But to limit global warming to 1.5C, as set out in the Paris Agreement of 2015, successive annual emissions drops of around 7-8 percent would likely be needed for the next decade.

Experts commenting on the findings said that the coronavirus emissions reductions came at the cost of huge economic shocks that cannot be used as a blueprint for how to tackle climate change.

Dr Joeri Rogelj, Lecturer in Climate Change and Environment at the Grantham Institute, Imperial College London, said: “None of this is good news for anyone. It is the symptom of a massive economic disruption caused by the pandemic and the measures to contain it. For the climate, this month-long wake in otherwise record-high emissions is entirely insignificant. Even worse, massive economic stimulus measures are now being announced and there is a high risk that short-sightedness will lead to governments [losing] track of the bigger picture, for example, by putting their money towards highly polluting sectors that have no place in a zero-pollution and zero-carbon society.”

Study suggests 50 days on, 30 days off lockdown strategy

A study has suggested that an efficient strategy of controlling coronavirus could be to have a rolling cycle of 50 day lockdowns followed by 30 days without, if it was continued for 18 months until a vaccine is found.

The study, published on Tuesday in the European Journal of Epidemiology, showed that such a “dynamic” approach to lockdown could strike the best balance between the need to control the virus and minimise economic impact, whilst also ensuring a high compliance to any measures chosen.

The researchers used mathematical models to look at different combinations of light lockdowns where only minimal social distancing measures are in place, fuller and stricter lockdowns, and then “relaxation” periods.

It found that light lockdowns followed by relaxation periods had some effectiveness, but that full periods of strict lockdown like that seen in March and April in the UK is the only way to fully protect health service overrun. It found a combination of 50 days on and 30 days off to be the most effective combination.

The study authors said: “Such a “schedule” of social distancing might be particularly relevant to low-income countries, where a single, prolonged suppression intervention is unsustainable.”

Study suggests how speaking can produce tiny saliva droplets

A study has used a new laser technique to show how the act of speaking can produce tiny droplets which stay in the air for up to 14 minutes – suggesting a potential path for coronavirus transmissions in small enclosed spaces.

In the research published last week in the journal PNAS, the authors said that their “observations confirm that there is a substantial probability that normal speaking causes airborne virus transmission in confined environments”. But experts commenting on the findings noted how only the fact that tiny droplets are produced by speech is shown here – not whether these droplets can cause coronavirus infection.

More work would be needed to prove that the virus itself can actually survive and be passed on through such tiny airborne droplets, experts said.

Previous studies have shown that coronavirus genetic material – but not necessarily the whole disease-causing virus itself – in the air is easily dispersed by just opening windows. If indeed there is a mechanism whereby functional virus particles are contained in aerosols and then passed on through things like breathing and speaking, it is still poorly understood.

Last week’s update can be found here.