TIME is running out to tackle the climate crisis and world leaders are still "falling short", Barack Obama has warned delegates in Glasgow. 

The former US President issued a rallying cry to young people during a speech at COP26, urging them to "stay angry" but to channel this into action.

He insisted: “The world has to step up and it has to step up now."

Mr Obama urged climate activists to "do a little more listening" to those who need persuading.

He was greeted by a huge crowd of excited delegates who cheered his arrival at the Glasgow summit yesterday.

Addressing the conference, Mr Obama said the US is back in the fight against climate change and took a swipe at the leaders of Russia and China for failing to attend.

He said the US is now "moving more boldly" after fours years of "active hostility" from the administration of Donald Trump.

He said: "I have to confess, it was particularly discouraging to see the leaders of two of the world's largest emitters - China and Russia - decline to even attend the proceedings, and their national plans reflect what appears to be a dangerous lack of urgency and willingness to maintain the status quo on the part of those governments. That's a shame."

Mr Obama said world leaders are "nowhere near where we need to be yet".

Despite the progress made at COP21 in Paris in 2015, he said, "most countries have failed to meet the action plans that they set six years ago, and the consequences of not moving fast enough are becoming more apparent all the time".

He said: “When it comes to climate, time really is running out.

"You heard the same message from world leaders last week. Now that they’ve left, here’s what we can report: meaningful progress has been made since Paris.

“The agreements made here in Glasgow, thanks to so many of you – including my friend [US climate envoy] John Kerry, who is tireless with his team – thanks to your efforts here in Glasgow we see the prospect of further progress.

“What is also true is that collectively and individually, we are still falling short.

“We have not done nearly enough to address this crisis, we are going to have to do more, and whether that happens or not to a large degree is going to depend on you – not just you in this room, but anybody who’s watching or reading a transcript of what I’m saying here today.”

Mr Obama said he “wasn’t real happy” about Mr Trump’s decision to pull the US out of the Paris climate agreement.

But he insisted: “The US is back. And in moving more boldly, the US is not alone."

He told delegates that to change the minds of fellow citizens, campaigners "have to do a little more listening". 

He added: "We can't just yell at them, or say they're ignorant. 

"We can't just tweet at them. It's not enough to inconvenience them through blocking traffic in a protest - we actually have to listen to their objections and understand the reluctance of some ordinary people to 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."

Moving away from fossil fuels, Mr Obama said, will have a cost, but it was for the more developed nations to ensure "the people most effected by the transition to clean energy aren't the ones baring most of the cost".

Addressing young people, he said: "I want you to stay angry, I want you to stay frustrated, but channel that anger, harness that frustration.

“Keep pushing harder and harder for more and more – because that’s what’s required to meet this challenge.

“Gird yourself for a marathon, not a sprint.

“For solving a problem this big and this complex has never happened all at once.”

He argued climate change should transcend day-to-day politics, adding: "There are times where I am doubtful that humanity can get its act together before it is too late – and then 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 – instead we are going to have to muster the will and the passion and the activism of citizens pushing governments, companies and everyone else to meet this challenge."

Mr Obama attacked the Republican Party in the US for showing “active hostility” to climate science, and insisted "saving the planet is not a partisan issue".

He said keeping the rise in global temperatures to 1.5C will not be easy, adding: "Getting people to work together on a global scale takes time, and right now that's time we don't have.

"So if we're honest with ourselves, yes, this is going to be really hard.

"The thing we have going for us is that humanity has done hard things before. I believe we can do hard things again."