We’re beyond debating the existence of climate change. Impacts we’re seeing now should compel us to reduce emissions further and start planning in earnest. It’s time to quit dithering.

We have been given a sobering glimpse into the speed of our changing climate and the vulnerabilities of our world. It turns out we must focus greater attention to the tropics, where so much of humanity and wildlife live, and to our oceans.

While policymakers posture, dither and deny, the unraveling has already begun.A sophisticated analysis, published in the premier scientific journal Nature by a team of young scientists at the University of Hawaii, Manoa, shows that impacts of climate change are already dramatic, with much more to come. While policymakers posture, dither and deny, the unraveling has already begun.

Many changes will continue in the years ahead, but we can slow them and buffer some of their impacts – if we act.

Using as a baseline the observed temperatures our world has known since 1860, when records first became reliable, biologist Camilo Mora and his co-authors sought to determine when future temperatures will move beyond the bounds of historical ranges. Others have examined how average temperatures will change; the Mora team examined how the full range of temperatures is changing, compared to historic ranges.

They come to the surprising conclusion that the tropics are particularly vulnerable. A shift out of the observed range of temperatures is expected as soon as 2020. When that happens, the coldest temperatures will be warmer than the hottest in the past. The implications for people, food supplies and biodiversity are tremendous.

Into the unknown

Over the next three decades, many of the rest of the world’s ecosystems – the deserts and jungles, the temperate zones, the polar regions – will likely move outside of temperature ranges that have nurtured life as we know it.

Within 35 years or so, most cities on earth will be living in a climate different from that upon which we have built our societies and civilization.

Examining changes other than temperature, the University of Hawaii team found that the oceans are already outside the historic range of variability for acidity. Oceans today are 30 percent more acidic than 150 years ago. And life in oceans is already showing signs of this stress.

Power to slow the changes

These findings and forecasts are startling, but there is some good news: This analysis found that if we reduce the amount of climate-altering emissions over the next few decades, we have the power to slow these changes significantly.

These results do not mean polar regions won’t see significant shifts. Or that ecosystems won’t prove flexible or resilient. But we have every reason to expect these climate changes will radically reorganize ecosystems, with unknown consequences to humanity.

We have every reason to expect these climate changes will radically reorganize ecosystems, with unknown consequences to humanity.As a professor of marine biology at Oregon State University and former administrator of the National Oceanic and Atmospheric Administration, and a professor of science and public policy at George Mason University, we see in this study a powerful message to citizens and policymakers alike: It’s time to take action.

From debating to documenting

A year ago, James Hansen, formerly of NASA, and his co-authors added a significant measure of understanding by looking at observed weather extremes over the last 30 years, particularly heat waves, compared to historical records. They found that we had lived through an exponential increase in outside-the-norm heat waves globally.

This study by Mora and his co-authors adds an important measure to our knowledge. We’re beyond debating the existence of climate change, and onto documenting and forecasting how quickly it takes shape around us. Shouldn’t we also be acting to slow the changes and to be prepared for what has been set in motion?