DW: The goal of the Paris Agreement is to limit global warming to well below two degrees Celsius above pre-industrial levels. Is limiting it to 1.5 degrees still possible?

Patricia Espinosa: It definitely is still possible. We are seeing a transformation in many areas of our societies at a pace we had not imagined just a few years ago. And at the same time new solutions are coming into the picture increasingly in different parts of the world. It is possible, but it requires really a very important political will. It requires action by each and every person in each and every society.

Is 1.5 degrees actually the goal, not 2 degrees?

Well, if you take the situation of countries like Fiji, which is presiding over this conference this year, for them it's 1.5. And we need to be ambitious.

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Many climate scientists agree we need to get to zero emissions or even negative emissions in the coming decades. Do you think that is actually achievable?

There is a lot of discussion about new and innovative solutions for that: how to get carbon emissions out of the atmosphere as well. We have to go toward climate neutrality. We have to be open and let ourselves be surprised by new developments and see if we really can find a way of going into a world of negative emissions.

Climate math shows we will have spent our carbon budget within a decade and time is running out for us to transition away from fossil fuels. Do you think we've reached a point where we have no choice but to consider other alternatives, for instance carbon capture and storage, or nuclear energy?

I believe we need to be open to all alternatives. Some countries are relying a lot on nuclear, others have decided to really rule out the nuclear option for different reasons.

In terms of [limiting] global warming, we need to be open to all possible solutions. However, we always need to bear in mind that any solution has to be reliable, has to be safe, has to really be done in a way that does not represent a threat to people.

Climate experts say a lack of political will and the influence of fossil fuel lobbyists are the biggest barriers to achieving the goals of the Paris accord. What is your plan as UN climate chief for dealing with these obstacles?

The fact that already 169 countries today - less than two years after the Paris Agreement was adopted - have ratified [the agreement], which is really a record number for a multilateral treaty like this, does show there is political will.

At the same time we are seeing a very rapid development in turning to renewable sources of energy. And this is happening also because the prices of other technologies are going down. So we are seeing now a world where in many countries in many places of the world, new and renewable sources of energy are competitive to fossil fuels.

Since taking office US President Donald Trump has been rolling back environmental protections, opting instead to support fossil fuel projects. What impact does the US withdrawal from the Paris Agreement have on achieving the goals of the accord given that the US is one of the top emitters of greenhouse gases? How will the world fill the gap?

I think it's important to recall the US will remain a party to the Paris agreement until 2020. So this means obligations and rights in the Paris Agreement remain fully in force for the [current] US government.

At the same time we have said since the very beginning this decision is disappointing. We have also always said we are willing to engage with them in trying to understand what their concerns are, what their objectives are with this withdrawal. And I would never give up the possibility or the hope that we can convince them to reconsider.

On the other hand what we are seeing is just an incredible amount of commitment and actions that are taking place in the US - not at the level of the federal government, but at the state level, at the level of cities, by private companies, by civil society. So some of the leaders of these constituencies are saying that regardless of what the US federal government [does], the US will comply with the commitments they had made before.

The solution to climate change is really quite simple: stop releasing carbon dioxide into the atmosphere. So why do you think it's so hard for people to get their head around the topic of climate change and why has action been so slow?

Stop emitting carbon emissions… well, even nature itself produces some carbon emissions, so it sounds easy, but it's not really. And also since the Industrial Revolution the world has developed and evolved in a way that is very intensive in carbon emissions, so it's really a huge transformation.

On the other hand, it's also a question of education. People who have grown up in a world where this was not a concern and suddenly start hearing about climate change - it's very difficult. It's a very, very abstract concept. So we need to work on making it very educational and very, very clear, in very simple terms.

I believe the very frequent extreme weather events we are now experiencing in different parts of the world are helping in raising awareness, but now there is an important part that we need to do in order to explain why that is linked to climate change, to global warming.

What needs to happen in order for the world to decarbonize?

We need to really get very serious about a transition toward new and renewable sources of energy. We have to be reminded that we still live in a world that relies a lot on fossil fuels, and that transition to new and renewable sources is not always and in all cases possible from one day to the next.

But if we manage to have a transition that combines the objectives of access to energy with well-being of people, with higher goals of development, we will be really going into the right [direction].

Patricia Espinosa is the Executive Secretary of the UN Framework Convention on Climate Change (UNFCCC).