Global efforts to arrest climate change and keep Earth liveable will fail without a jumbo-sized effort from India to halt emissions growth that could wipe out ambitious carbon reduction targets elsewhere.
But one thing India doesn't need, its leaders have made clear, is lectures from the West on what path to take.
The world's third-biggest carbon emitter, already home to 1.3 billion people, is projected by the UN to become the planet's most populous nation by the middle of the decade.
Crucially for its carbon footprint, its urban population is set to rise the size of Los Angeles each year, totalling 270 million people by 2040, according to the International Energy Agency (IEA).
They will all need homes, built with energy-intensive concrete and steel, vehicles to drive, goods to consume and air-conditioning to survive India's ever-harsher summers.
To meet the associated electricity demand over the next 20 years, India could need to add a power system the size of the European Union's, the IEA believes.
"All roads to successful global clean energy transitions go via India," it said in a recent report. "The stakes could not be higher, for India and the world."
- Sunny side up -
These are sobering statistics ahead of US President Joe Biden's virtual climate summit this week and UN talks in Glasgow set for November.
But India bristles at being told what to do, particularly by Western countries that bear far more historical responsibility for climate change and still have much higher per capita carbon footprints today.
"They emitted and therefore the world is suffering. India is suffering because of actions of others," Environment Minister Prakash Javadekar thundered last week.
"We will not allow anybody to forget it."
India is also acutely aware that climate change is happening: melting Himalayan glaciers, a water crisis, rising temperatures and more frequent cyclones are already wreaking havoc.
Air pollution from vehicles, industry, power generation and farming was meanwhile blamed for over a million premature deaths nationwide in 2019.
And unlike many other countries, India is on track to exceed its voluntary goals under the 2015 Paris climate agreement.
These include improving the economy's emissions intensity 40 percent by 2030, and growing the share of non-fossil fuels in power generation to 60 percent -- well above its 40 percent pledge.
India has also set the ambitious target of reaching 450 gigawatts of renewable capacity by then, including 280 gigawatts from solar power, which is already highly competitive on price compared to coal.
Solar currently accounts for less than four percent of electricity generation, and coal 70 percent. By 2040 solar and coal are on track to each account for around 30 percent, the IEA says.
A recent report by UK energy group Ember even suggested that India's use of coal for power generation may have already peaked three years ago.
- Offsetting Europe -
But carbon emissions are still on track to grow 50 percent by 2040, enough to offset entirely the projected fall in emissions in Europe over the same period.
Emission reductions are possible with major upgrades to India's power infrastructure, including battery storage for solar energy.
But the main reason for the CO2 increase is industry -- making all that steel and concrete for India's booming cities -- and transport, with 25 million more trucks expected on the roads by 2040.
The government is still building more coal power plants and awarding contracts to mine more coal. Already India's output is 700 million tonnes per year, second only to China.
There has been speculation that India -- following the US, EU and China -- might announce a target date for net zero emissions, but this may require changes too far-reaching for the government to stomach.
A study by the Council on Energy, Environment and Water (CEEW) think-tank said that to achieve net zero by 2050, the share of coal, oil and gas would have to tumble from 73 percent in 2015 to just 5 percent.
It would also cost half a million mining jobs, higher electricity prices and, since Indian Railways relies heavily on coal freight for income, higher fares for millions of train passengers, said Vaibhav Chaturvedi from the CEEW.
A more realistic path would be greater use of existing technologies to cut emissions, like electrifying more trains and vehicles, greener construction materials, rooftop solar panels, using more hydrogen fuel, and capturing emissions for storage.
But this will require $1.4 trillion more than currently in the pipeline, the IEA says -- much of which needs to be provided by richer nations.
"India should do more but it should also get support from the international community," Harjeet Singh from Action Aid Climate told AFP.
"The international community is listening to only half of the story... My worry is that if there is no real money, we will not see real action."