I once made Ed Miliband wince. I persisted with a question at a public meeting, asking him to do more about climate change, and he wasn't pleased. But looking back he had already made a great achievement – getting the UK's Climate Change Act passed, which happened 10 years ago.

Prince Charles and David Attenborough are both speaking up this week about how urgent it is to take action on climate. They're worth listening to, but the people who influence me most aren't famous. They're farmers in the world's poorest countries and I've heard from so many that life's getting harder. There are more floods, more droughts, and less rain when the crops need it. I particularly remember one grandmother from Malawi saying that when she was young, each home in her village had a grain store to keep their maize harvest in. Her grandchildren don't know what a grain store looks like because nobody harvests enough maize to need one any more.

So back in the early 2000s I campaigned for the Climate Change Act and was overjoyed when we got it. I remember how uniting it was, inside and outside parliament. Ed Miliband was the environment minister who led the Act energetically, and Gordon Brown backed it as prime minister. David Cameron was in his green phase and supported it as leader of the opposition.

The only real battle I remember was the target. We pushed the government to reducing emissions by 80 per cent by 2050 compared to what they were in 1990. It helped that some reductions had happened already and that it was led by the facts of the time – this really was the amount all developed countries needed to cut their pollution by to limit warming to a safe (ish) level of two degrees. The science has since moved on and we now know we need to keep warming to 1.5 degrees – and to do this our economy needs to reach 'net zero' emissions before 2050.

So 10 years on, what difference has the Act made? We've successfully cut our emissions by 43 per cent from 1990-2017 to meet the first two carbon budgets set by the Act, and we're on track to meet the third. Our big success has been stopping burning coal for electricity, very fast: we've gone from coal producing nearly half of Britain's electricity in 2012 to just five per cent this year. We've shut some coal power stations and we've promised to close them all by 2025. We've achieved this by replacing coal with gas and renewables – we're the world leader in offshore wind – and by using a bit less electricity. And we've promised to reach net zero emissions this century.

But that was the easy bit: the future is looking less rosy. The independent Committee on Climate Change says we'll miss the fourth and fifth budgets unless the government does more than it's currently planning to. Its approach to climate change puzzles me in recent years. It seems to think hard about what the most important things it needs to do are, does them, and then go out of its way to stamp out most other progress.

We're aiming to use less fossil fuel but at the same time we've started fracking to get hold of more of it, which doesn't make sense. We're cutting subsidies for electric cars just before they've got cheap enough for the mass market. And if we do build a third runway at Heathrow then emissions from flying would rise and probably make our Paris Agreement promise to decarbonise impossible to keep.

The UK could easily have done far more. We've stopped building onshore wind turbines except on Scottish islands. Given that many of our power stations are near retirement age and onshore wind is now the cheapest way to build new electricity capacity, as well as being very low carbon indeed, this is perverse.

However, the Act has also had great symbolic power internationally. It said the UK was serious about climate action and set an example others could copy to show that they were too. The first of those was Scotland, which passed its own, more ambitious Climate Change Act the following year; the most recent is Peru, this year. This gave the UK credibility in international climate negotiations, which helped get the historic global Paris Agreement in 2015.

Our Climate Change Act was a time when God answered our prayers and our government really listened to the voices of ordinary people, even ordinary people in other countries. I'm encouraged each time I think about it. But I need that encouragement to keep praying and working for us to cut our emissions faster, to protect ourselves and our global neighbours. Tearfund won't stop until poverty stops, even if sometimes we make a politician wince.

Ben Niblett is a senior campaigner at Tearfund.