Joe Biden is pushing by far the most aggressive plan to address climate change in U.S. presidential history. His path reflects the convergence ofscience, energy and activism trends.

Why it matters: The culmination shows the new permanence the problem has gained on the campaign trail despite President Trump’s dismissal of it. Although this election is more about other issues, its outcome will significantly shape future efforts on this front.

Flashback: It’s worth documenting where the Democratic Party and its presidential politicians have been in the past to note the significance of where the party is today.

• While in the White House, then-President BarackObama extolled the environmental benefits of natural gas and the jobs it created during the first part of his administration. Today, it's controversial and Biden does not praise it.
• Obama started souring on the energy source toward the end of his presidency, but he still approved massive increases in liquefied natural-gas exports, a trend Trump takes credit for today.
• A week after Trump won the 2016 election, the Obama administration released a plan to cut America’s carbon emissions 80% by 2050, seen at the time as a widely ambitious goal (not to mention imminently irrelevant with Trump’s victory).

How it works: Over the last decade, and especially in just the last few years, the scientific and economic landscapes have changed significantly to push Democratic politicians — and other parts of our society, like investors — to support more aggressive positions on climate change.

The biggest changes:

• The plummeting costs of wind and solar energy.
• Growing concern about the environmental footprint of natural gas.
• Increasing scientific urgency about climate change, especially an October 2018 United Nations report calling on world leaders to limit global warming to 1.5 degrees Celsius relative to preindustrial levels.

Where it stands: The Biden campaign, along with an increasing number of companies, states and countries, are now calling for a net-zero carbon goal by 2050, far more aggressive than the Obama administration’s 2016 goal.

• Although the 1.5-degree limit goal is considered almost impossible, it nonetheless tightened what had previously been the political goalpost of limiting the rise to 2 degrees. (The bigger the rise, the less aggressive the efforts have to be to achieve it.)
• A half-degree seems tiny, but it's massive on a planetary scale.
• The lower costs for wind and solar have also made it easier to support more aggressive renewable energy policies and dismiss natural gas.

“It’s not often that scientific reports have profound effects on people’s thinking,” said John Podesta, a Democratic insider on an advisory board of a climate advocacy group created earlier this year. “But I think the 1.5 report of the [United Nations] told policymakers that they had a completely different goal they had to manage toward.”

The intrigue: In response to these scientific and economic changes, a youth-led social movement was born, which have helped create groups like the Sunrise Movement.

• The Sunrise Movement has often been credited with pushing Biden to the left, but the bigger influence has been the changing scientific and economic landscape, which has affected both activism and political positioning.

Between the lines: Biden has embraced aggressive goals also pushed by the progressive side of his party, including a $2-trillion spending plan, but when it comes to specific technologies he has actually staked out a more centrist position.

• The campaign is supporting existing nuclear power and carbon capture technologies. The latter could likely prolong society’s use of oil and natural gas.
• This support persisted despite opposition from grassroots activists. Campaign spokesman Matt Hill said the support for these comes because “the scale of the climate crisis requires us to leave all of the options on the table.”
• Varshini Prakash, Sunrise Movement co-founder and a member of a task force giving recommendations to the campaign, said in a recent interview: “The Biden team was fairly adamant that nuclear and [carbon capture] should be part of the platform ... We were clear about where we stood.”

But, but, but: More aggressive climate policies bring risks, including energy affordability and reliability. California has imposed electricity blackouts as heat waves have led to greater demand for energy compared to supply.

• These blackouts are due, at least in part, to the state's poor handling of an increase of wind and solar energy, experts say. That's because other energy sources need to be available to jump in since it's not always windy or sunny.
• Trump and other Republicans argue that if Democrats' renewable-energy policies come to pass, the nation will face the same problems as California.

What they’re saying: “I was worried about this, to be honest,” said Julian Brave NoiseCat, vice president of policy and strategy at the liberal Data for Progress.

• But then he pointed to polling conducted by his group that indicated a majority of respondents didn't associate renewable energy with the blackouts.
• Polling conducted by interest groups should be viewed with scrutiny, but it nonetheless shows the perspective emerging from the progressive left wing of the Democratic Party.

Go deeper: Natural gas is a question mark in Joe Biden’s climate plan