As 2017 drew to an end, becoming one of the three hottest years on record, my native United States conversely experienced dangerously frigid, Arctic weather, leading to intense debate about how climate change could also be the cause of extreme cold.

Although the big freeze was predictably seized upon by climate sceptics to scorn the veracity of global warming, the jury on whether climate change triggered the extreme weather is far from out. Research into the complex dynamics of a warming Arctic, the polar vortex, the jet stream and how the interplay between them drives global weather patterns continues.

The freezing weather also followed a brutal onslaught of hurricanes, floods, wildfires, and deadly droughts that had already marked 2017 as a year to remember, a year in which global CO2 emissions also started to rise again.

Seen in this light, there can be no doubt that we are pushing our planet to the brink, as the World Economic Forum's Global Risks Report 2018 has warned.

In the US, President Donald Trump's own National Oceanic and Atmospheric Administration (NOAA) also found 2017 was the costliest year ever for weather and climate disasters, with the cumulative economic costs coming to over $300bn. Worldwide, insured losses alone reached hundreds of billions according to the world's largest reinsurance company, Munich Re - a total that doesn't include the trillions of dollars in economic losses. Nor, critically, does it factor in health impacts and loss of life.

But these extremes are the new normal in a world that has unnaturally warmed 0.85 degrees Celsius on average over the past 20 years above preindustrial levels.

It's why a special report currently being drafted by the Intergovernmental Panel on Climate Change (IPCC) to examine how the world can stabilise global warming at 1.5 degrees Celsius is so keenly awaited.

Achieving 1.5 degrees was the aspiration committed to in the Paris Climate Agreement - an ambitious goal that only made it into the final accord thanks to the tireless and passionate advocacy of the world's most vulnerable nations.

For small island states like Tuvalu or Dominica, the difference between 1.5 and 2 degrees of warming is existential. For all nations, every fraction of a degree matters - no population would avoid the impacts of 2 degrees of warming. So the IPCC report is far from academic: it's a matter of life and death; of prosperity versus suffering.

Recent peer-reviewed science - which will be drawn on for the IPCC report - tells us that stabilising temperatures at 1.5 degrees is tremendously hard, but still achievable. But it's only possible if we take serious action now. This means transformative change - and not only in the energy sector. We must protect and restore our forests, defend our oceans and transform our agriculture as well.

What this means is that we need to stop building new coal plants and start shutting down existing ones, replacing them with carbon-free wind and solar, which can, when paired with newly-affordable battery storage and improved transmission, already deliver reliable, affordable electricity around the clock. We need to stop drilling for oil to propel personal vehicles, given that the technology exists to plug these cars into a cleaner grid while more and more people can ditch expensive vehicles forever with better mass transit and ridesharing options.

We need to ensure that our woodlands, salt marshes and mangroves, so important as natural stores of carbon as well as for the preservation of biodiversity, are protected from further degradation and given space to recover and that our oceans are healthy and teaming with life.

All these things need to happen together. And the good news is that these actions will pay for themselves - by creating jobs, reducing public health costs and avoiding climate impacts.

Although we're on the cusp of major change, particularly in the global energy system, we must move beyond incremental change and achieve a positive transformational shift in the world's energy and land-use systems.

The sooner we act, the better and the speed of change is accelerating. REN21's Renewables 2017 Global Status Report showed that unprecedented price reductions in solar energy were again reported in 2016, while onshore wind power is the most cost-effective option for new grid-based power in an increasing number of markets.

These developments give me hope that unproven and potentially unsustainable technological fixes proposed for carbon dioxide removal or geoengineering of the atmosphere will not be needed to achieve a 1.5C world. Many carbon removal technologies would result in unacceptable ecological and/or social impacts and give no guarantee they will permanently remove CO2 from the atmosphere. And no geoengineering proposal will change the need for a dramatic decarbonisation of our economy. Waiting to act will only make the job much more difficult, disruptive and expensive.

The next few years are crucial. We have a moral, ethical responsibility to seize the small window of opportunity we still have to make bold and lasting change to deliver true climate security for us all.

The views expressed in this article are the author's own and do not necessarily reflect Al Jazeera's editorial stance.