A UN climate expert believes India is on the cusp of becoming a global leader in the field of sustainability. There are three things that, for me at least, best characterise modern India. And it is because of these qualities that I'm so convinced that the country is on the cusp of becoming a global leader in climate action and sustainability. Firstly, from independence to today, India has always steered a unique course -confident in its own path. It's also a nation where enterprise and innovation flourish, and where learning is held in such high esteem. Thirdly, its strong civil society, built on the moral foundations laid down by the Mahatma, forms the backbone of the world's most vibrant democracy. So what does any of this have to do with the massive, global challenge of climate change Of course it would be foolish to try to distil India into a few characteristics and make a prediction, but for me it all comes down to a simple equation: How can India deliver on its development ambitions, guarantee long-term energy security and lift hundreds of millions of people out of poverty and into a vibrant economy This is where renewable energy fits in so squarely. It's an historic opportunity that ticks every box, and something India is embracing because it can guarantee independence, fuel innovation and answer public demands for sustainable, inclusive growth. A shift away from dirty coal fire stations will bring enormous benefits to public health, and therefore huge savings. After all, a healthier workforce is a stronger and more productive workforce. In addition, renewables installations that are already deployed in India have shown their flexibility in adapting to the Indian context. In Tamil Nadu, which basks in sunshine for roughly 300 days of the year, Adani Power's solar farm - which came on line just last year - is the world's second-largest such installation. Clearly a success, the state is looking to expand and sell excess power to neighbouring states. Rajasthan and Andhra Pradesh, blessed with similar sunshine the space for panels, are also leading the change. In Kerala, engineers made Kochi airport self-sufficient with solar, which they experimented with because of high electricity prices - a great example of a mini-grid solution that has inspired airports or similar installations around the world. And in villages across India, farmers and villages are discovering the joys of off-grid solar pumps and lighting solutions. From 2014 to 2016, India quadrupled solar-generation capacity - and meanwhile set itself the ambitious target of generating 100 GW by 2022 - when it marks 75 years of independence. Electricity costs are plummeting, which in turn will unleash untapped economic capacity. And India is right where it should be: on the cutting edge of innovation. This, I'm convinced, will have an enormous knock-on effect. Indian demand for panels brings economies of scale to manufacturing, which in turn drives down prices. The huge investment opportunities bring competition, which in turn drive innovation - the kind that will improve panel efficiency and storage solutions. At this rate, the costs argument alone is so compelling that everything from mega coal plants all the way to gas-guzzling transport systems will no longer make economic sense. The result will be an India that is energy independent, armed with the know-how and innovative minds to manage mega energy projects and therefore compete on the world stage, all the while delivering on national needs for clean air and a healthy population. In fact, I cannot think of a single reason why India should not continue on this path. As for the moral arguments - the Prime Minister spelled these out loud and clear when he said it would be a “crime” not to act on climate change. I've also seen the power and energy of Indian civil society: not so long ago I was on a beach near Mumbai, getting my hands dirty with lawyer and friend Afroz Shah. The Versova beach clean-up has invigorated global concerns over plastic waste, and the fate of our oceans. It has inspired the country, telling us clearly that demands for a clean environment cannot be ignored. As India steers a path to low-carbon growth, public support will be strong. It was with all this in mind that listened to President Trump announce his decision to withdraw from the Paris Agreement, followed by the inevitable voicing of fears that the progress we've seen will be undone. Certainly, the US decision is a disappointment, but the response we've seen has shown these fears to be unfounded. US cities and states, as well as the private sector, have redoubled their commitments. We've seen continued strong support from the European Union, from China and India, and many other nations. As such, the leadership vacuum is being filled. Let's be in no doubt: India is not steering this path on behalf of the White House, or any other country for that matter. And let's not be in any doubt as to the scale of the challenge. But the motives that underpin Indian action are sound. It's doing so because its right for the economy, right for national development and right for the Indian people. This embodies the very purpose of the Paris Agreement: rather than tie up nations with binding targets, the purpose is to unleash the kind of innovation we need to see. Those who embrace the change will come out healthier, and those who don't will be left behind. In India, just like in many other parts of the world, the train has already left the station. Erik Solheim is Executive Director of the United Nations Environment Programme.