You know the routine by now.

The world’s leaders meet for another round of climate change negotiations — this time in Paris in December. They reaffirm the goal of keeping global warming below 2 degrees Celsius. They pledge reductions in their greenhouse gas emissions. We hear that this is our last chance to save the earth from rising sea levels, more powerful tropical storms, increasing desertification, water scarcity, species extinctions and, if we reach dangerous tipping points, the irreversible melting of Greenland and Antarctic ice sheets, pushing eventual sea level rise to tens of meters. After reaching an agreement, governments then fail to meet their targets, the Arctic sea ice and glaciers continue to melt and we go about our business with no sense of urgency until the next round.

This pattern has to stop. First, we have to face the facts. Then we have to take action that is up to the challenge we face.

1. It is time to admit we have failed to stop climate change, failed our children and future generations. Not only is climate change already happening, but the pace of change in reducing greenhouse gases is too slow to keep the earth from warming more than 2 degrees Celsius. The problem is that CO2 stays in the atmosphere for centuries. Even if we stopped using fossil fuels today, much of the CO2 in the atmosphere and the warming it already has caused are here to stay. The world, thus, has a fixed budget for emissions to stay within tolerably safe limits, and that budget — around 600 gigatons more carbon — is rapidly being used up. China’s emissions still are rising — partly because we have outsourced our manufacturing there — as are India’s, and the pace of reduction in the developed countries is not fast enough to bring total emissions down, much less at the pace needed to stay within our budget.

To make matters worse, former National Oceanic and Atmospheric Association head James Hansen has been arguing that even a 2 degree Celsius rise over preindustrial levels would be disastrous, and we need instead to limit warming to not much more than 1 degree Celsius — we already are past 0.8 degree Celsius. He and a team of scientists just released a study asserting that major glacial melting is likely in this century, potentially causing the sea level to rise as much as 10 feet in 50 years or less.

Think how many of the world’s great coastal cities would become uninhabitable — not only Venice and New Orleans but London, Shanghai, New York and many others. To keep this from happening, our carbon budget should be closer to 100 gigatons. At current emission levels, we will exhaust this budget before 2030, not after midcentury. By this latest assessment, then, time is running out.

Of course, scientists will debate these latest findings. Many will take comfort in the uncertainty.

Shouldn’t we instead act on the assumption that the worst may happen, just as we insure our homes against fire?

2. In principle, we still can save the earth and future generations from the worst consequences of global warming. But it will require more rapid reduction of carbon emissions than will emerge from the Paris talks, on the order of 6 percent per year globally, and since the emissions of China and other developing countries will not peak for a decade or more, that means even higher annual reductions in the developed countries. For comparison, the EPA’s Clean Power plan, perhaps the most the Obama administration can do without congressional action, aims for a 13 percent reduction of total U.S. emissions compared to 2005, by 2030 — less than 1 percent per year.

Congressional action is unlikely before the next election, but to make climate change a defining issue in the campaigns, we need to be lobbying legislators, talking to our friends and neighbors and defending the EPA initiative at the state level, so that by 2017 it will be possible to legislate a carbon fee that reflects the true environmental cost of fossil fuel. That will discourage the use of fossil fuels and enable renewables to compete in the market. If the revenue is returned to citizens as dividends, a majority of households will gain financially despite the rise in energy costs. Nevertheless, the transition will not be easy. We must not only shift to renewable energy but also curtail our consumption.

But if we all are in it together, what we give up will not feel like poverty so much as change and the opportunity to leave a prosperous and sustainable world to our grandchildren.

Michael Howard is a professor of philosophy at the University of Maine. He is a member of the Maine chapter of the national Scholars Strategy Network, which brings together scholars across the country to address public challenges and their policy implications.