Twenty-six years after the founding of the Intergovernmental Panel on Climate Change (IPCC), the Nobel Prize-winning group of scientists and world governments has released a new synthesis report that warns in its strongest tones yet that climate change must be dealt with. None of the findings are surprising—they have been released in earlier assessments throughout the year—but the terms in which they are written are the starkest yet, especially given this is coming from the conservative scientific community.

“Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia. The atmosphere and ocean have warmed, the amounts of snow and ice have diminished, and sea level has risen,” reads the new synthesis report, which notes that it is “extremely likely” humans are the major driver behind current global warming, i.e. scientists are 95 to 100 percent certain.

The report finds that global warming will likely continue for centuries, even if greenhouse gas emissions dropped to zero today. Yet humanity now has to decide between a pace of warming that human society—and much of nature—can adapt to and one that wreaks irreversible harm.

“Warming by the end of the 21st century will lead to high to very high risk of severe, widespread, and irreversible impacts globally,” reads the report, in its strongest statement on this to date. It also notes that impacts are not far-flung in the future, but already being felt around the world.

However, the report was not all gloom-and-doom. Instead, it noted that humanity—and their governments—have a clear choice regarding the future.

“We have the means to limit climate change,” R. K. Pachauri, Chair of the IPCC, said. “The solutions are many and allow for continued economic and human development. All we need is the will to change, which we trust will be motivated by knowledge and an understanding of the science of climate change.”

Indeed, recent research has shown that instead of devastating the global economy—an argument often used by climate change deniers—dealing with climate change would actually be quite cheap. An IPCC report released in April found that combatting climate change would decrease global growth by just 0.06 percent over the century. However, this report didn’t take into account the economic benefits of switching to renewable energies, such as new jobs, pollution reductions, and greater price stability for electricity.

“The world can afford to fight climate change. This will neither cripple economies nor stop development—to the contrary. What is clear is that inaction will be much more costly, even when considering conservative estimates,” said Samantha Smith, the head of WWF’s Global Climate and Energy Initiative.

Still, it’s a tall order. The IPCC, which some activists have criticized as being too conservative, says that greenhouse gas emission must be cut by 40 to 70 percent by 2050 in order to avoid catastrophic climate change. Moreover, by the end of the century, emissions will have to be near zero, meaning that unless carbon capture and storage makes good, fossil fuels as an energy source must go the way of whale blubber.

Thickly packed sea ice in the Arctic from a photo taken in 1949. One day thick, stable sea ice in the Arctic will likely be a thing of the past as the Arctic is warming around eight times faster than the rest of world according to a new analysis. Photo by: Rear Admiral Harley D. Nygren.

If concerted action isn’t taken to lower greenhouse gas emissions however, global temperatures could rise as much as five degrees Celsius (nine degrees Fahrenheit) by the end of the century, creating a world wholly different from the one we live in today.

Warnings over global warming have been ratcheting up for decades as the science—and the understanding of the threat posed—has become stronger.

“We do not need any more reports—we need action. We don’t have any more time to coddle fossil fuel billionaires or politicians who will eschew responsibility at every corner,” said Sierra Club Executive Director Michael Brune.

In September, over a half a million people worldwide marched for action on global warming according to organizers, including 400,000 in New York City, where global leaders were gathering for discussions on climate change. It was the largest climate march in history and the biggest march in New York City since protests against the Iraq War.

“Science has spoken. There is no ambiguity in their message,” U.N. Secretary-General Ban Ki-moon during the launch of the report. “Leaders must act. Time is not on our side.”

Leaders will have their next opportunity to act in December. That’s when governments from around the world meet in Lima, Peru for the annual Conference of the Parties (COP). This year’s conference is pivotal as it’s meant to build momentum for a global agreement in 2015 in Paris.