Obama swipes at Trump for 'four years of active hostility' on climate in Glasgow speech

But as much as Obama expressed regret for former President Donald Trump's "four years of active hostility towards climate science" and the climate denialism which defines the modern Republican Party, he expressed a deeper, broader worry that politics all over the world is falling short of what needs to be done to save the planet.

"I recognize that we're living in a moment when international cooperation has atrophied—in part because of the pandemic, in part because of the rise of nationalism and tribal impulses around the world, in part because of a lack of leadership on America's part for four years on a host of multilateral issues," Obama said.

Obama's speech came a week after President Joe Biden's own appearance at the conference, during which he explicitly apologized for Trump's abandonment of the Paris climate accords. And it came amid major international doubts that Biden, Congress or America is actually serious about climate change, no matter what Obama said.

Obama said that the US is reengaging with the world on climate, and he sought to convince the world that the US has stayed on track, even during the Trump years, as questions persist at the conference over how the US plans to make up for lost time.

"Of course, back in the United States, some of our progress stalled when my successor decided to unilaterally pull out of the Paris Agreement in his first year in office. I wasn't real happy about that," Obama said.

But he said these lost years are not reason to lose faith in the power of what global cooperation can achieve, or even in the US' commitment to climate. Despite Trump, Obama said, "the American people met our original commitment under the Paris Agreement."

"Not only that, but the rest of the world stayed in the deal. And now with President Biden and his administration rejoining the agreement, the US government is once again engaged and prepared to take a leadership role."

'Vote like your life depends on it'

The former President pleaded that climate change should be the one issue which transcends politics. And Obama said he has his own doubts this is possible, which he tries to fight back.

"We are nowhere near where we need to be yet. For starters, despite the progress that Paris represented, most countries have failed to meet the action plans they set six years ago," he said.

"As I'm sure is true for all of you, there are times when I feel discouraged, when the future seems bleak, and I am doubtful that humanity can get its act together before it's too late," Obama said "And images of dystopia start creeping into my dreams. And yet, whenever I feel such despondency, I remind myself that cynicism is the recourse of cowards. We can't afford hopelessness."

Obama's appearance at an international conference is already an unusual move for a former president, as is his public criticism of "my successor" -- the closest Obama came to saying Trump's name. Also unusual is his criticism of current foreign leaders, as he called out Chinese President Xi Jinping and Russian President Vladimir Putin for skipping the COP 26 entirely. He called that decision "particularly discouraging," adding "their national plans reflect what appears to be a dangerous absence of urgency, a willingness to maintain the status quo, on the part of both those countries."

Addressing the younger people in the audience, Obama said "you're right to be frustrated."

"For most of your lives, you've been bombarded with warnings about what the future will look like if we don't address climate change," Obama said. "And you've grown up watching many of the adults who are in a position to do something about it either act like the problem doesn't exist or refuse to make the hard decisions necessary to address it."

Picking up on a theme he has repeatedly hit on the campaign trail back home, Obama pleaded for young people not to give up on politics.

"Vote like your life depends on it," he said, since "the cold, hard fact is that we will not have more ambitious climate change plans unless governments get behind them."

But he warned that young people need to rethink their approach. He said that first and foremost, young people need to "vote the issue."And he picked up on another theme he's expressed before: that today's youth mistakes online activism and insular virtue signaling for making a difference.

"Protests are necessary to raise awareness. Hashtag campaigns can spread awareness. But to build the broad-based coalitions necessary for bold action, we have to persuade people who either currently don't agree or are indifferent to the issue," Obama said. "We have to do a little more listening. We can't just yell at them, or tweet at them -- it's not enough to inconvenience them by blocking traffic through protests. We're going to have to listen to the objections and reluctance of ordinary people that see their countries move too fast on climate change. We have to understand their realities, and work with them so that serious action on climate change doesn't adversely impact them."

Obama pressed the point that local governments and many privates businesses stayed committed to hitting the Paris accord targets, despite Trump's withdrawal of the federal government. They should believe in Biden's commitment now, he added, and said he has faith a larger Build Back Better plan with more extensive climate measures will soon pass Congress, despite the hold-ups in Washington last week which led to a vote on only one of the infrastructure bills.

Nonetheless, Obama praised the "meaningful progress" made by world leaders through the agreements reached last week in Scotland—such as those to combat methane emissions and deforestation, as well as those signed by two dozen countries, not including the United States, to end public subsidies for fossil fuels and pledging to end the use of coal completely.

While in Scotland, Obama will also meet with several groups of climates leaders, as well as business and philanthropic leaders, and local elected officials. He was introduced by an Obama Foundation leader who is a Northern Mariana Islands representative, and he will spend time with several others during the trip.

Obama had championed addressing environmental issues while in office, but Trump -- a longtime climate crisis denier -- attempted to remove many of the policy guardrails installed by the Obama administration to limit the emissions of greenhouse gases. Since taking office, Biden has been reversing many of these actions by the Trump administration and has made ambitious pledges to tackle the climate crisis.

Notably, the climate summit is taking place five years after the Paris Agreement took effect. In 2015, after the COP21, more than 190 countries signed onto the agreement at the time to limit the increase in global temperatures to well below 2 degrees Celsius above pre-industrial levels, but preferably to 1.5 degrees.

Biden reentered the Paris Agreement after former Trump pulled the United States out of it, and apologized to his fellow world leaders in remarks on the first day of COP26.

"I guess I shouldn't apologize, but I do apologize for the fact that the United States -- the last administration -- pulled out of the Paris Accords and put us sort of behind the 8-ball," the President said last week in Glasgow.

The-CNN-Wire™ & © 2021 Cable News Network, Inc., a WarnerMedia Company. All rights reserved.