GEOFF BENNETT: Welcome to the "NewsHour."

Scientists warned today that climate change is warming the planet to the point where it is causing irreversible damage in some parts of the world.

AMNA NAWAZ: The new report from the United Nations Intergovernmental Panel on Climate Change, or IPCC, found that, within a decade, the world is likely to miss its goal of holding global warming to 1.5 degrees Celsius or 2.7 degrees Fahrenheit.

If or when the planet reaches that level, scientists say Earth will pass tipping points that will lead to catastrophic environmental damage, including dangerous sea level rise, entire species going extinct, and even greater suffering in many nations, especially the poorest.

U.N. Secretary-General Antonio Guterres said the time to act is now.

ANTONIO GUTERRES, United Nations Secretary-General: Humidity is on thin ice and that eyes is melting fast.

The rate of temperature rise in the last half-century is the highest in 2,000 years.

Concentrations of carbon dioxide are at their highest in at least two million years.

The climate time bomb is ticking.

AMNA NAWAZ: For a closer look at the report and what can be done to change the direction the planet is headed, I'm joined by Katharine Hayhoe, climate scientist at Texas Tech University and chief scientist for the Nature Conservancy.

Katharine Hayhoe, welcome back to the "NewsHour."

That is strong language from Antonio Guterres there, saying humanity is on thin ice, the climate time bomb is ticking.

This is about as dire and urgent a report and a warning as we have heard.

Why now?

KATHARINE HAYHOE, Climate Scientist, Texas Tech University: It is completely justified.

We scientists have been warning of the impacts of climate change on humans and all other life on this planet for decades.

Yet our carbon emissions continue to rise.

As the IPCC report says, the window of opportunity we have to make decisions that will lead us to a better future is closing rapidly.

AMNA NAWAZ: That increase in global average temperatures, we have been trying to keep to 1.5 degrees Celsius, that -- it's often referred to as the tipping point.

We seem to be hurtling towards that right now.

Just as we cross that threshold, if we are to cross that threshold, help us understand, what does that mean for life here on Earth?

For our viewers who have kids or grandkids, how would their lives be different?

KATHARINE HAYHOE: One-and-a-half degrees is not a magic threshold or a tipping point.

Rather, it is a goal that we have set ourselves, knowing that the science is very clear.

Every bit of warming matters.

Every little bit that the planet warms carries additional cost with it.

So, how much do we need to do?

As much as possible.

When?

As soon as possible.

Why?

Because we will all benefit from that action.

AMNA NAWAZ: And, if we don't, paint that picture for us.

What looks different here on Earth?

KATHARINE HAYHOE: Well, we are already seeing the impacts here today in the way that climate change is loading the weather dice against us.

We know we have always had droughts and floods and hurricanes and heat waves.

But, in a warming world, they're getting stronger and more dangerous.

And they're impacting all of us.

But they are particularly affecting those who are vulnerable and marginalized the most.

The warmer the world gets, the more it endangers our food supply, our water supply, the safety of our homes, our own health, our economy and supply chains, the natural environment.

Every aspect of life on Earth, including our life on Earth, is at risk the warmer this planet gets.

AMNA NAWAZ: So, this report says, in order to shift course, we would need to slash greenhouse gases in half by 2030, and stop adding carbon dioxide to the atmosphere altogether by the early 2050s.

Do you see that happening?

KATHARINE HAYHOE: It is possible.

If we have the will to do so, we can accomplish it.

The problem we have today, though, is, we still, many of us, don't really understand how this issue affects us here and now.

And we don't understand that the majority of the solutions we need are already in our hands.

And that's what the IPCC report makes very clear, that these changes are already affecting us, our homes, our food, our water, our economy, our cities, our states, and the solutions, efficiency, clean energy, investing in nature, adapting and building resilience, many of those solutions are already here today as well.

The only question at this point is, what are we waiting for?

If we wanted to accomplish this, we could.

AMNA NAWAZ: There are some who've said there have been worse climate scenarios predicted before, some who had said there could be a warming of four degrees or more sooner, which now looks unlikely.

There will be some who will look at this and say, well, could these predictions be wrong as well?

KATHARINE HAYHOE: The previous predictions were not wrong.

But the uncertainty is us.

The predictions were for what is going to happen, depending on the choices we make.

Prior to the Paris Agreement in 2015, the world was heading towards a future that was between four to five degrees Celsius warmer than today.

And you might say, well, that doesn't sound so bad.

It's four or five degrees outside or inside warmer.

But think of it in terms of the human body.

The temperature of the planet has been as stable as that of the human body over the course of human civilization this planet.

If our body is running a fever of one or two degrees Celsius or three or four or five or six degrees Celsius, that is life-threatening.

So we have already, thanks to the Paris Agreement, changed -- reduced the amount of change that we expect in the policies that have already been adapted by at least a degree.

But we still need more, because every bit of warming carries a cost with it.

AMNA NAWAZ: These warnings, as you say, have been coming for decades.

So I'm curious why you think it is that the climate threat has resided, in many people's minds, as a future threat, not necessarily an imminent one.

KATHARINE HAYHOE: For many of us, it's because we haven't seen the impacts with our own eyes.

We have heard about them.

We know what's happening to polar bears or Antarctica or ice sheets, but we're not seeing it here and now.

Well, that has changed.

Over the last year, at least one in three Americans were personally affected by the way that climate change is making our extreme weather more severe.

We might live somewhere where sea level is rising, where hurricanes are getting stronger, where wildfires burn in greater area, where the summers are now dominated by record-breaking heat waves.

Climate change is no longer a future issue.

It is right here where we live.

It is right now.

And the time to fix it is also here now.

AMNA NAWAZ: That is Katharine Hayhoe, climate scientist and chief scientist for the Nature Conservancy.

Thank you for joining us.

KATHARINE HAYHOE: Thank you so much for having me.