LONDON — As Britain prepares to host a landmark climate summit in Glasgow this week, the milestones of its own evolution to a more climate-friendly economy are on vivid display along the railroad line from London to Scotland.

Near Gainsborough, a river town 150 miles north of the capital, one of Britain’s last coal-fired power plants still spews carbon dioxide and other gases into the air. Another 150 miles north, off the coast of the seaside port of Blyth, the slender blades of five turbines in an offshore wind farm turn lazily in the breeze.

The two plants, both owned by the French utility giant EDF, illustrate how far Britain has come. The coal station, restarted recently to cover a shortfall in electricity, is slated to be taken out of operation next year, while the company plans to install experimental floating turbines in the waters off Blyth.

“We’re talking about a huge transition,” said Paul Spence, the director of strategy and corporate affairs at EDF, referring to Britain’s goal of being a carbon-neutral economy by 2050. “A lot of things need to happen to keep the lights on.”

climate meeting, known as COP26, it has a credible claim to being a global leader in climate policy. The birthplace of the Industrial Revolution, Britain became the first country to legally mandate reductions in greenhouse-gas emissions through the Climate Change Act in 2008. Its high-tech windmills and superannuated smokestacks are only the most visible evidence of a three-decade campaign.

Having built the world’s largest offshore wind industry, Britain has reduced emissions by 44 percent from 1990 levels. Its target to cut them by at least 68 percent by 2030 is one of the most ambitious of any major economy, according to the Climate Action Tracker, a scientific analysis of the policies of countries.

If Britain achieves that target, which is far from clear, it would be one of a handful of countries doing enough to fulfill the key goal of the Paris Agreement: limiting the long-term rise in the planet’s temperatures to 1.5 degrees Celsius.

showdown with striking coal miners in 1984. By crushing the union and slashing subsidies for the coal industry, Mrs. Thatcher accelerated Britain’s search for alternative energy sources, namely natural gas.

“She got rid of the coal miners for a combination of political and economic reasons,” said Tom Burke, the chairman of E3G, an environmental think tank, and a former government adviser. “But it gave the U.K. a degree of freedom of action that wasn’t available to other countries.”

she said to the United Nations.

Mrs. Thatcher planted the seed for a bipartisan cause, as Conservative and Labour governments sought to burnish their green credentials. British diplomats played key roles in brokering climate deals in Rio de Janeiro and Kyoto, Japan. Britain installed climate attachés in its embassies around the world.

In 2006, a British government adviser, Nicholas Stern, produced a seminal study of the economic effects of climate change, which framed the debate before the 2009 summit in Copenhagen and set the stage for the Climate Act, passed under a Labour prime minister, Gordon Brown.

When the Conservatives came to power in 2010, they viewed climate policy as a way to appeal to younger voters, many of whom viewed the Tories as a tightfisted party in thrall to business interests. Parliament created a climate change committee, which prodded the government to adopt policies that would help Britain meet its goals. Several of its policies were mimicked by fellow European Union members. “We basically ran the E.U. on climate policy,” Mr. Burke said.

Then came the Brexit vote in 2016, and “we lost our most important tool for influencing other countries, which was the E.U,” he said.

Mr. Johnson, who once scoffed that wind farms would “barely pull the skin off a rice pudding,” now speaks about climate change with the zeal of the converted. Allies say he has been convinced of the need for action by his third wife, Carrie Johnson, who campaigns against plastic pollution.