Everyone heaved a sigh of relief when the ink dried on the Paris Agreement. Finally, we thought, the world's leaders had committed themselves to doing something about climate change. But behind all the fanfare, scientists have not been quite so optimistic. And now, as of this year, they've arrived at a startling consensus: the Paris Agreement is deeply flawed - and we're going to need a better one.

The problem is that the Paris deal is built on the assumption that highly speculative technologies are going to save us from climate catastrophe; specifically one called BECCS, or bioenergy with carbon capture and storage. The idea behind BECCS is to grow massive tree plantations around the world to absorb CO2 out of the air, then harvest the trees, convert them into pellets, burn them in power stations for energy, capture the CO2 that's emitted from the smokestacks and store it deep under the ground. Voila: net-negative emissions.

But BECCS has never been proven at scale; it is science fiction. In order to work as the Paris deal hopes, it would require plantations covering two to three times the size of India - a third of the planet's arable land. Not only would this make it impossible to feed the world's population, it would also be an ecological disaster. A team of researchers led by German scientist Vera Heck has found that BECCS would trigger a 10 percent loss of global forest cover and a 7 percent loss in biodiversity. It also risks driving further water scarcity, soil depletion, and chemical loading into ecosystems.

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In other words, BECCS might help with climate change, but only by pushing us into other crises. If we used BECCS within the safety zone of planetary boundaries, it would sequester at most 1 percent of annual global emissions. That could be a useful part of an overall strategy, but it's a far cry from the saviour technology that the Paris deal assumes.

Michael Orbersteiner, the Austrian scientist who first proposed BECCS in 2001, has criticised policymakers for "misusing" his idea. He warns that while it might help as a last-ditch option in case climate feedback loops turn out to be worse than expected, it should never be relied upon as a primary strategy. But that's exactly what the Paris Agreement does. Instead of making the deep emissions cuts that we need, our leaders are assuming that geo-engineering will save us sometime later this century, using BECCS as an excuse to carry on with the status quo.

This is not only wishful thinking; it's actively dangerous. In a paper published in Science in 2016, Professor Kevin Anderson and Glen Peters point out that relying on BECCS is "an unjust and high stakes gamble": if it fails, "society will be locked into a high-temperature pathway".

Scientists from all quarters are sounding the alarm. In 2014, fifteen scholars questioned the credibility of BECCS in the pages of Nature Climate Change, noting that "its widespread deployment in climate stabilisation scenarios might become a dangerous distraction" from the imperative of reducing emissions. The following year, another 40 scholars stated in the same journal that reliance on negative emissions technologies - not only BECCS but also other ideas like direct air capture and enhanced weathering - is "extremely risky". Many more have come forward with the same conclusions.

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The consensus on this is now rock solid. Last month the European Academies' Science Advisory Council, a body that brings together the national science academies of EU states, published a report condemning the Paris Agreement for its reliance on BECCS and other negative emissions schemes. The Council urges that instead of betting on speculative tech fantasies, we should turn to more down-to-earth plans like regenerative farming and reforestation, while - most importantly - making aggressive cuts to emissions.

If we take BECCS out of the equation, things get more serious. Rich nations will need to reduce their emissions by more than 10 percent per year. The tricky bit is that while we can manage some of this by investing heavily in renewable energy, it's ultimately going to require that we step off the treadmill of endless economic growth and consumerism - and fast. Our leaders are desperate to avoid this conclusion. But the science is clear: we can't rely on technology alone. It's time for a new economic system. For the Paris Agreement to work, this truth needs to be at its heart.

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