I have struggled to visualize global warming in personal terms. This seemed impossible until I read the October 2013 issue of Nature (Nature 502, 183–187 (10 October 2013)). The projected timing of climate departure from recent variability features a new predictive model, developed by combining the 39 major contemporary climate models in order to best fit the available data. The authors predict that if there is no change in greenhouse emissions, global temperatures will continue to escalate for the next 34 years, culminating in worldwide “unprecedented climate change,” meaning that every subsequent year will be hotter than 2005, the hottest year ever recorded. This will first unfold in the tropics, where species are the most plentiful and the most vulnerable to small changes in climate: Kingston in 10 years, Singapore in 15, Mexico City in 19, Cairo in 23, Phoenix and Honolulu in 28, and finally the whole world in 34 years.
- "Here we 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. Using 1860 to 2005 as the historical period, this index has a global mean of 2069 (±18 years s.d.) for near-surface air temperature under an emissions stabilization scenario and 2047 (±14 years s.d.) under a ‘business-as-usual’ scenario. Unprecedented climates will occur earliest in the tropics and among low-income countries, highlighting the vulnerability of global biodiversity and the limited governmental capacity to respond to the impacts of climate change. Our findings shed light on the urgency of mitigating greenhouse gas emissions if climates potentially harmful to biodiversity and society are to be prevented."
Thirty-four years is a much shorter timeframe than I had ever previously imagined. In personal terms, it means that my own daughters, ages 9 and 11, will witness ever-rising temperatures, escalating climate events, food and water insecurity, increasing species extinctions, and millions or billions of desperate climate refugees. As adults my girls will be living in an entirely new climate. In the worst case scenario, such unprecedented climate change could be only 20 years away.
But the authors also present a more hopeful scenario: we might have up to 75 years to meet the challenge if we drastically decrease our carbon emissions now. By slowing the pace of disaster, a second and possibly even a third generation could have a chance to rescue the biosphere. It is difficult to visualize the scope of this challenge: in order simply to survive, humanity would have to engineer sustainable supplies of food and water as the new climate evolves, combat newly evolving diseases, and eventually supporting surviving portions of disrupted ecologies to create a newly rebalanced web of life.
The stakes are enormous, but what are the odds? We cannot predict the specific conditions that the next generations will be facing; it is difficult even to imagine solutions that might work in the unprecedented new climate. We can hope that our efforts might buy them a little more time, providing our children and grandchildren a better chance to respond and to survive.