Within hours of taking office last week, President Donald Trump made good on his pledges to wind back the United States’ climate action – including withdrawing the US from the Paris Agreement.

This political show comes barely a week after 2024 was revealed as the world’s hottest year and following the catastrophic Los Angeles fires. The fires directly killed 20 people; potentially many more will die from toxic smoke and other after-effects.

The science is clear: achieving net-zero emissions by 2050 is humanity’s only hope of achieving some measure of climate security. It’s time to think deeply on our chances of getting there.

Here, I outline a few reasons for pessimism, and for hope.

Reasons for pessimism

1. The data doesn’t lie

The landmark Paris Agreement, signed by 196 nations in 2015, aimed to limit global temperature rise to well below 2°C above pre-industrial levels while pursuing efforts to limit it to 1.5°C. Achieving that requires reaching net-zero emissions by mid-century.

Yet nearly a decade after the agreement, global emissions continue to rise. The Global Carbon Budget estimates a record-high 37.4 billion tonnes of CO₂ was emitted last year.

And 2024 was not just the hottest year on record – it was the first year to exceed the 1.5°C temperature threshold.

It’s not too late to change trajectory. But sadly, the data show the bathtub is fast filling, and the tap is still running hard.

2. Renewable energy rollout is too slow

Renewable energy deployment is increasing and the price is falling. But it’s not happening fast enough.

According to the International Energy Agency, clean energy investment must more than double this decade if the net-zero goal is to be reached by 2050. In particular, clean energy investment in developing countries must increase significantly.

Richer nations – which are largely responsible for the stock of emissions in the atmosphere driving the climate problem – are failing to help developing countries make the clean energy shift. At the COP29 climate talks in Baku last year, developed nations agreed to give only US$300 billion (A$474 billion) a year in climate finance to developing countries by 2035. It is nowhere near enough.

3. The net-zero smokescreen

Net-zero emissions is not the same as zero emissions. It allows some industries to keep polluting, if equivalent emissions are removed from the atmosphere elsewhere to keep the balance at zero.

This means nations that are purportedly committed to the net-zero goal can continue with business as usual, or worse.

In 2023, for example, then-British Prime Minister Rishi Sunak announced 100 new oil and gas licences in the North Sea, saying it was “entirely consistent” with his government’s net-zero goal. The same logic has allowed Australia’s environment minister, Tanya Plibersek, to approve new coal mines.

Both decisions came from governments that have pledged commitment to reaching net-zero – yet both are clearly making the goal harder to achieve.

These are just a few of the reasons to feel pessimistic about getting to net-zero – there are many more.

Barriers exist to extracting the critical minerals needed in low-emissions technology. Differences in human relationships to nature means we will never reach full agreement on how to respond to environmental risk. And globally, there is rising mistrust in international agreements and institutions.

But it’s not all doom and gloom. Here’s why.