Climate change futures: health, ecological and economic dimensions

8 | EXECUTIVE SUMMARYOther non-linear impact scenarios include:• Widespread diebacks of temperate and northernforests from drought and pests.• Coral reefs, already multiply stressed, collapse fromthe effects of warming and diseases.• Large spikes occur in property damages from a riseof major rivers. (A 10% increase in flood peakwould produce 100 times the damage of previousfloods, as waters breach dams and levees.)• Severe storms and extreme events occurringsequentially and concurrently across the globeoverwhelm the adaptive capacities of evendeveloped nations; large areas and sectors becomeuninsurable; major investments collapse; andmarkets crash.CCF-II would involve blows to theworld economy sufficiently severeto cripple the resilience that enablesaffluent countries to respond tocatastrophes. In effect, parts ofdeveloped countries would experiencedeveloping nation conditions for prolongedperiods as a result of naturalcatastrophes and increasing vulnerabilitydue to the abbreviated return timesof extreme events.Still, CCF-II is not a worst-case scenario.A worst-case scenario would include large-scale, nonlineardisruptions in the climate system itself —slippage of ice sheets from Antarctica or Greenland,raising sea levels inches to feet; accelerated thawingof permafrost, with release of large quantities ofmethane; and shifts in ocean thermohaline circulation(the stabilizing ocean “conveyor belt”).Finally, there are scenarios of climate stabilization.Restabilizing the climate will depend on the globalscaleimplementation of measures to reducegreenhouse gas emissions. Aggressively embarking onthe path of non-fossil fuel energy systems will takeplanning and substantive financial incentives — notmerely a handful of temporizing, corrective measures.This assessment examines signs and symptomssuggesting growing climate instability and exploressome of the expanding opportunities presented by thishistoric challenge.APPLYING THE SCENARIOSIn choosing how to apply the two impact scenarios,we have focused on case studies of specific healthand ecological consequences that extend beyond themore widely studied issue of property damagesstemming from warming and natural catastrophes. Ineach case study, we identify current trends underwayand envision the future consequences for economies,social stability and public health.Infectious diseases have resurged in humans and inmany other species in the past three decades. Manyfactors, including land-use changes and growingpoverty, have contributed to the increase. Ourexamination of malaria, West Nile virus and Lymedisease explores the role of warming and weatherextremes in expanding the range and intensity of thesediseases and both linear and non-linear projections forhumans and wildlife.The rising rate of asthma (two to threefold increase inthe past two decades; fourfold in the US) receivesspecial attention, as air quality is affected by manyaspects of a changing climate (wildfires, transporteddust and heat waves), and by the inexorable rise ofatmospheric CO 2in and of itself, which boostsragweed pollen and some soil molds.We also examine the public health consequences ofnatural catastrophes themselves, including heat wavesand floods. An integrated approach exploring linkagesis particularly useful in these instances, since thestovepipe perspective tends to play down the very realhealth consequences and the manifold social andeconomic ripples stemming from catastrophic events.Another broad approach of the CCF scenarios is tostudy climate change impacts on ecological systems,both managed and natural. We examine projectionsfor agricultural productivity that, to date, largely omitthe potentially devastating effects of more weatherextremes and the spread of pests and pathogens.Crop losses from pests, pathogens and weeds couldrise from the current 42% to 50% within the comingdecade.