Climate variability for the coming century
Planning for a sustainable future is obviously made much more difficult when a rapidly changing climate is added to the equation. Planning effective policy and development goals will depend greatly on where we find ourselves in ten, twenty, thirty or fifty years.
A recent paper published in the journal Nature, authored by Camilo Mora and his colleagues at the University of Hawaii's Department of Geology, focuses on the question of when we can reasonably expect Earth's future climate to diverge from its historical norms of variability. As stated in the paper's abstract, the research aims to "present a new index of the year when the projected mean climate of a given location moves to a state continuously outside the bounds of historical variability under alternative greenhouse gas emissions scenarios."
The research uses the period from 1860 to 2005 as the historical baseline utilizing the complete set of available climate models for its analysis. Looking at seven different climate variables, including temperature, ocean acidity and precipitation, Mora and his team constructed a timetable of what they term "climate departure" for any spot on earth. The study lays out two projection paths, one for "business as usual" and another, more optimistic projection that "reflects a strong and concerted reduction in carbon dioxide emissions."
"We're providing a new metric on when ongoing climate change will lead to environments like we have never seen before," Mora told reporters, "when the coldest year of the future will be warmer than the hottest year in the past."
Tropics and poor countries first to reach "climate departure"
While the polar regions are considered the climate "canary in a coal mine," already exhibiting the most dramatic changes, it is in the tropics where Mora's research suggests climate departure will first occur, as much as 15 years, on average, before the rest of the globe. "Our study shows that the tropics, not the poles, will be experiencing unprecedented climates first," say Mora.
Mora explains the reason for this is because the tropics typically have relatively little climate variability from year to year. On the other hand, polar regions are normally subject to a much broader range of extremes. More refers to this as "double jeopardy" for climate change:
"The largest absolute changes are happening at higher latitudes," he said. But these polar extremes still don't fully break from historical norms. It's a different scenario at lower latitudes. "Unprecedented climate is happening more rapidly at the tropics."
Based on a business as usual scenario, New Guinea will enter climate departure as soon as 2020, at which time the region will enter a new state of climate variability never before experienced by any human population.
The global average for climate departure in the business-as-usual scenario is 2047, 34 years hence. The more optimistic scenario, where society makes a determined effort to effectively reduce greenhouse gas emissions, pushes climate departure back to 2069 (still leaving New Guinea in climate departure by 2025). Mora explains that the optimistic scenario reflects CO2 stabilized at 538 parts-per-million (ppm), well above the 350 ppm that scientists say is required to avoid the worst consequences of climate change. Earlier this year CO2 concentrations hit 400 ppm.
Whether we follow a path of business-as-usual (there seems little to indicate otherwise) or take on the challenge and aggressively reduce emissions, the study shows that climate departure will occur in the relatively near future.
Oceans in crisis
Mora's research paints an even more urgent picture for the oceans. According to the study, ocean acidity reached levels outside historic norms back in 2008, give or take three years. The research concurs with a recent study by scientists at Oxford University showing the rate of ocean acidification is higher than at any time in the past 300 million years.
Change is inevitable
Whether the world hits climate departure a few years before 2050 or a few years after, it is clear the world is changing. We still have time to mitigate and adapt, but, given the already observed extreme weather events that steadily are becoming the norm, the sooner we begin to work together to reduce carbon emissions and deforestation, the sooner we adapt to the change already baked into the system, the more time we'll have to stave off climate departure and the better our chances for a viable future.
An interactive map of future climate change impacts is available on Dr. Mora's website.