Famous buildings and structures have switched off their lights to highlight change during Earth Hour, plunging landmarks in Moscow, Sydney and Beijing into complete darkness.
The blackout is set to last from 8.30pm to 9.30pm tonight as part of an international event organised by WWF to urge action to save the planet.
Andy Ridley, who was one of the driving forces behind Earth Hour when it began in Sydney, Australia, in 2007, said the world has the chance to do something positive for the planet even during this current crisis.
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A composite picture shows residential and commercial buildings stand on the island of Hong Kong with lights on (left) and switched off (right) for the Earth Hour in Hong Kong, China today
It comes as some UK cities have seen significant drops in air pollution as the shutdown to tackle the coronavirus pandemic disrupts work and travel, analysis suggests.
Assessment of data from roadside monitoring sites in York, Birmingham, Glasgow, London and Manchester has revealed reductions in key pollutants nitrogen dioxide and tiny particles known as 'PM2.5'.
Due to the coronavirus pandemic, the WWF said it is not organising public gatherings - instead, supporters are encouraged to join in with online events.
Mr Ridley, speaking in an interview with Steven Day, the co-founder of renewable energy provider Pure Planet, said that 'the one thing we should be taking out of this is we have the capacity to act if we decide we are going to'.
He added that there is a 'power of action when you get a mass engagement'.
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Pictured here are juxtaposed images of St Basil's Cathedral in Moscow, Russia before and during Earth Hour 2020, a WWF environmental campaign event annually held on the last Saturday of March to raise awareness of climate change by encouraging people to turn off their lights and electric appliances for an hour
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A combination photo shows the Sydney Harbour Bridge and the Opera House seen before they are plunged into darkness (left) and being plunged into darkness (right) for the Earth Hour environmental campaign on March 28, 2020
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A composite photo shows the National Stadium (Bird's Nest) before (left) and during (right) the Earth Hour in Beijing, China today. Earth Hour is an annual event in which lights are switched off in major cities around the world to draw attention to energy consumption and its environmental effects
Mr Ridley also said that the world's current battle with coronavirus 'does clearly show the capacity for us to deal with things' and he advised anyone who may no longer be able to get outside that 'the biggest thing' is to 'remember how good it is to be out and how worth it that is.'
He also said in the interview: 'Greta (Thunberg, the teenage environmental campaigner) was right when she said if governments decide to do something then we can do something.
The excuse has always been it's too hard, but we have just proven it isn't too hard.
So what happens at the end of this, how do we rethink what's going on?'
People walk and run to take their daily exercise allowance in Battersea Park in London today as pollution in the city decreases
Signs on the side of a road alert motorists to 'Stay Home' and that they should only travel if it is 'Essential', in Manchester. The city has seen a reduction in pollution
A graph shows how much lower pollution in London is this year compared to the years 2015 to 2019
A number of landmarks across England are expected to take part in the grassroots movement, including London's The Shard, Blackpool Tower and Old Trafford in Manchester.
The annual hour of darkness aims to highlight the impact humans are having on the planet through climate change, pollution, plastic and food production.
Katie White, executive director of advocacy and campaigns at WWF-UK, said: 'These are really unprecedented times, and I know a lot of people are looking for ways to connect and feel connected.
'In this global health crisis, now is a pivotal time for us to work together to safeguard our future and the future of our planet.'
Pictured: The drastic reduction in pollution levels in London between March 2019 (top) and March 2020 (bottom)
Bristol's Clifton Suspension Bridge will go dark between 8.30pm and 9.30pm tonight as part of the international event organised by WWF
London hotspots like Piccadilly Circus and Covent Garden - which have been deserted in the past week due to the Covid-19 outbreak - are also expected to take part
Bristol's Clifton Suspension Bridge will go dark, while London hotspots like Piccadilly Circus and Covent Garden - which have been deserted in the past week due to the Covid-19 outbreak - are also expected to take part.
More than 7,000 cities in some 170 countries were estimated to have taken part last year.
WWF is also encouraging supporters to join in online by tagging £EarthHour, while the organisation said it is running a series of virtual events - such as a silent disco and a Facebook quiz.
Ms White said: 'While - first and foremost - our thoughts are with those affected by coronavirus, and those who are working so hard in healthcare and other vital services, many millions of us are working and operating from our homes.
'Taking part in Earth Hour this year feels very timely - a time when millions unite around the world to show they care about the future of our planet.
'In these difficult times, It's an opportunity to inspire hope.'
It comes as analysis by scientists from the University of York of data from the London Air Quality Network and UK Automatic Urban and Rural Network has shown that the pollutants had fallen to levels lower than the average of the past five years due to the coronavirus crisis.
Monitoring of European cities, many of which are in lockdown over the pandemic, by the European Environment Agency (EEA) also reveals large decreases in air pollution, particularly nitrogen dioxide.
The reduction in nitrogen dioxide in UK and European cities is likely to be caused by lower levels of traffic, experts said.
Sources of PM2.5 include road transport, industry and fuel burning.
Professor James Lee from the Department of Chemistry at York and the National Centre for Atmospheric Science (NCAS) said: 'These are the two air pollutants that have the biggest health impacts on people.
'From our analysis, pollution levels are clearly lower than the average of the previous five years.
'I would expect them to drop even further over the coming weeks.
'We will continue to analyse the data and potentially take in more sites to build a bigger, more accurate picture of the situation.'
Britain's coronavirus death toll rocketed by 260 to 1,019 today as the UK suffered its worst day yet and saw a huge spike in victims
Ambulance staff and health workers outside the ExCel Center in London. The NHS is anticipating a Coronavirus 'tsunami' as the peak of infarction rates nears
The data will need to be carefully analysed to pinpoint the exact cause of the decline, the scientists warn, as many things can affect air pollution, including local weather, new regulations and human activity.
Air pollution causes an estimated 40,000 early deaths in the UK each year.
It is linked to health problems including stroke, heart disease, lung cancer and disease, and respiratory diseases and infections, as well as stunting the growth of children's lungs.
Experts have warned that the health benefits of reduced air pollution and lower exposure as people stay off the streets and in their homes in the shutdown may not offset mortality from Covid-19 and health problems caused by isolation.
Data from local monitoring stations analysed by the EEA reveals big drops in nitrogen dioxide in some cities across Europe.
A police officer talks to a cyclist at Regents Park in London, during a lockdown over the spread of coronavirus
People walk to get their daily exercise allowance in Battersea Park in London today
The average concentrations of NO2 for the past four weeks have been at least 24% lower than four weeks earlier this year. The average concentration during the week of 16-22 March was 21% lower than for the same week in 2019.
Here, there has been a constant decline in NO2 pollution over the past four weeks. The average concentration during the week of 16-22 March was 47% lower than for the same week in 2019.
The average NO2 concentrations for the past four weeks were 26-35% lower than for the same weeks in 2019.
The average NO2 levels went down by 40% from one week to the next. Compared with the same week in 2019, the reduction was 55%.
The average NO2 levels went down by 56% from one week to the next. Compared with the same week in 2019, the reduction was 41%.
The average NO2 levels went down by 40% from one week to the next. Compared with the same week in 2019, the reduction was 51%.
In Milan, northern Italy, average concentrations of the pollutant over the past four weeks are at least 24% lower than over four weeks earlier this year.
Rome's pollution levels over the past four weeks were 26-35 % lower than for the same weeks in 2019, the EEA said.
Cities in other European countries have also seen major reductions in nitrogen dioxide where lockdown measures have been implemented during the week of March 16-22.
Barcelona's pollution levels fell 40% from one week to the next, and were down 55% compared to the same week in 2019, while Lisbon has seen a 41% drop in nitrogen dioxide week-on-week and is down 51% compared to the same week last year.
Hans Bruyninckx, EEA executive director, said: 'The EEA's data shows an accurate picture of the drop in air pollution, especially due to reduced traffic in cities.
'However, addressing long-term air quality problems requires ambitious policies and forward-looking investments.
'As such, the current crisis and its multiple impacts on our society work against what we are trying to achieve, which is a just and well-managed transition towards a resilient and sustainable society.'
Yesterday, satellite images from the European Space Agency showed a massive drop in air pollution levels across European cities due to coronavirus isolation measures.
New data captured by the ESA Copernicus Sentinel-5P satellite shows a strong reduction in nitrogen dioxide concentrations over major European cities.
The change in the amount of NO2 in the atmosphere is particularly stark in Paris, Milan and Madrid, according to the ESA.
The coronavirus has been spread around the world and to combat this spread and ease demand on health services countries have gone into lockdown.
Copernicus has mapped air pollution levels across Europe since the outbreak of the virus and found a 'significant drop' coinciding with new lockdown measures.
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The new maps shared by the European Space Agency show a dramatic difference in NO2 levels across Spanish cities including Madrid and Barcelona
The change in the amount of NO2 in the atmosphere is particularly stark in Paris, Milan and Madrid (pictured), according to the ESA
The images show a dramatic difference in NO2 levels across all European cities, particularly in Spain, France and Italy coinciding with the lockdown measures.
It matches similar figures from the London Air Quality Network that showed a sharp drop in air pollution levels over the UK capital city.
This is due to a notable drop in traffic levels on the streets of cities across Europe.
GPS maker TomTom said the percentage of roads congested with traffic in London dropped from 71 per cent this time in 2019 to just 15 per cent yesterday.
The UK capital's levels of ultra-fine particulate matter, known as PM2.5, are currently around half that would be normally recorded at this time of year.
This matter is produced in a large part from vehicles and burning fossil fuels.
Scientists from the Royal Netherlands Meteorological Institute (KNMI) have been using data from Copernicus Sentinel-5P satellite to monitor both weather and pollution over Europe.
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On the left of this picture is the level of NO2 over France in March 2019 and you can see a drop in the number of dark red areas from the left