It used to be said of a good politician that they were able to make the weather. The metaphor has acquired a literal sense in recent years as humanity’s effect on the climate has become clear. In early July, downpours and flash floods hit parts of Glasgow. As I begin a two-day visit to the city tomorrow, the world is looking ahead to November, when countries’ representatives will gather in Glasgow for the 2021 UN climate change conference (Cop26). The world is looking to Britain, as host of the summit, to deliver. We cannot afford to miss this moment, but I fear we will.

The urgent need for a coherent response is in front of our very eyes. In recent weeks flash floods have immobilised parts of Britain, Germany and China. Towns built on rivers have been destroyed and there have been frightening scenes of train commuters trapped underground in rising water. Record heatwaves and fires have ravaged parts of North America. All over the world, unusual weather events show that dystopia is not on the horizon. It is here today, all around us.

This is a test of the prime minister’s ambition for “global Britain”. Based on the government’s actions so far, or lack of, it’s implausible that this ambition will be met. In 2015, the Paris agreement achieved unprecedented global commitments. Paris defined the “what”; an agreement at Glasgow is now needed to supply the “how”. Paris set the collective ambition to limit the rise in global temperature to 1.5C above pre-industrial levels. This now needs to be translated into concrete action, coupled with an unequivocal promise to deliver. Time is short and history will not forgive a failure to act now.

Yet at this vital moment, Boris Johnson is missing in action, while his climate spokesperson is busy advising people to freeze their leftover bread. When the issues at stake are so large it really is irresponsible for the response to be so small. This is a challenge that encompasses diplomacy, economics, finance, and targeted investment.

A credible government now would be demonstrating serious ambition. Look at President Biden in the United States, who says that when people talk about climate, he thinks about jobs, and who has a plan for green investment. Labour has the same ambition. We have a plan to support jobs while cutting the substantial majority of our emissions by the end of this decade. But we need to act immediately. The Office for Budget Responsibility points out that acting early could mean we need an average of annual investment of just 0.4% of national income between now and 2050.

The first step in that ambition should be a GBP30bn investment in a green recovery from the pandemic. That investment would create hundreds of thousands of secure jobs across the whole country. It would ensure that we buy, make and sell more in Britain. We would be rejuvenating our car industry while helping it move to the production of electric cars. We would be powering our homes with offshore wind turbines built in Britain and we would be manufacturing clean steel to build our schools, hospitals and railways. Labour would pass a Clean Air Act to improve the air we breathe and the water in our rivers. Every decision we made – from spending to infrastructure – would have to pass a robust “net zero and nature test”, to make it consistent with our environmental ambitions.

Under the Conservatives, we are a long way off our climate targets. Among the G7 countries, the UK’s green recovery and job creation plans rank sixth. Rather than substance, Johnson is responding with a cabaret of soundbites. He has promised to make us the “Saudi Arabia of offshore wind” yet all he has delivered is offshored jobs, with turbines built thousands of miles away from Britain. He promised a green housing revolution before axing his own green homes grant. And as proven by the chaos around a new coalmine, his own advisory climate change committee has warned that this government is blundering into “high-carbon choices”.

Forty years ago, a Conservative government ensured that the effects of de-industrialisation were felt very unevenly across the nation. Without good leadership, the same will be true of decarbonisation, with good, unionised, secure jobs replaced by insecure work. Under my leadership, Labour’s green transition would be a fair transition. That is the promise of a Green New Deal: an economy that is greener and fairer at the same time.

With 100 days to go before the end of Cop26, the world needs a truly historic result in Glasgow. Often, when politicians talk about the climate crisis, they make an emotional plea for action on behalf of our children’s generation. As a parent, I know first-hand the desire to give your children a better future. But the future is already with us. It’s desperate that we have a government so firmly rooted in the past.

• Keir Starmer is the leader of the Labour party