Increasing temperatures and rising sea levels demand that we act now if we are to minimize the huge expense associated with a warming world. As the White House explains in the introduction to the report:
"The scientific consensus is that these changes, and many others, are largely consequences of anthropogenic emissions of greenhouse gases that have led to a warming of the atmosphere and oceans."If we continue with business as usual we are on track to exceed the internationally agreed upon upper threshold limit increase of 2 degrees Celsius. Allowing warming to reach 3 degrees Celsius could cause damage amounting to 0.9 percent of global economic output each year. These costs come from deleterious impacts on public health and biodiversity, as well as physical impacts from rising seas and more severe storms, droughts and wildfires.
If the world warms by 4 degrees Celsius the costs will escalate to 1.2 percent of global output. The warmer we get the greater the costs.
Here are four key points contained in the report:
1. Immediate action substantially reduces the cost of achieving climate targets. Taking meaningful steps now sends a signal to the market that reduces long-run costs of meeting the target. Such action will reduce investments in high-carbon infrastructure that is expensive to replace and will spur development of new low- and zero-emissions technologies. For both reasons, the least-cost mitigation path to achieve a given climate target typically starts with a relatively low price of carbon to send these signals to the market, and subsequently increases as new low-carbon technologies are developed and deployed. An analysis of research on the cost of delay for hitting a specified climate target suggests that net mitigation costs increase, on average, by approximately 40 percent for each decade of delay.
2. Climate change stemming from delayed action creates large estimated economic damages. If delayed action causes the mean global temperature increase to stabilize at 3° Celsius above preindustrial levels, instead of 2°, that delay will induce annual additional damages of 0.9 percent of global output. To put this percentage in perspective, 0.9 percent of estimated 2014 U.S. GDP is approximately $150 billion. The next degree increase, from 3° to 4°, would incur greater additional annual costs of 1.2 percent of global output. These costs are not one-time: they are incurred year after year because of the permanent damage caused by additional climate change resulting from the delay.
3. The possibility of abrupt, large-scale, catastrophic changes in our climate increases the need to act. These large-scale events include the melting of the West Antarctic ice sheets and other ice sheets – which would cause large degrees of sea level rise – as well as the release of additional methane through thawing of permafrost, which would accelerate global warming. These and other potential large-scale changes are irreversible on relevant time scales – if an ice sheet melts, it cannot be reconstituted on any societally relevant timescale – and they could potentially have massive global consequences and costs. For many of these events, there is thought to be a “tipping point,” for example a temperature threshold, beyond which the transition to the new state becomes inevitable, but the values or locations of these tipping points are typically unknown.
4. Enacting meaningful change in climate policy is analogous to purchasing climate insurance. Much like other insurance purchased by individuals and businesses, paying mitigation costs now reduces the odds of a large-scale catastrophic change in climate. And, unlike conventional insurance policies, climate policy that serves as climate insurance is an investment that also leads to cleaner air, energy security, and benefits that are difficult to monetize like biological diversity.
Graphics - Cost of Delaying Action to Stem Climate Change
Action on Climate Change a Cost Benefit Analysis
Climate Change: Frequency, Costs and Mortality (World Meteorological Organisation)
Businesses Feel the Heat from Declining Labor Productivity
Economic Benefits of Combating Climate Change (IIED)
Economic Costs of Combating Climate Change (IPCC)
Reducing Fossil Fuel Use: The Longer We Wait the More it will Cost
Infographic - How Much Would it Cost to Go Green Globally?
Graphic - The Cost of Mitigating Climate Change
The Financial Costs of Biodiversity Loss
Extreme Weather and the Costs of Climate Change
The Costs of Global Warming
The Costs of Climate Change Related Flooding
Graphs - Global Cost of Flooding
The Costs of Flood Damage will Rise Along with Sea Levels
Balken Flooding and the Costs of Climate Change
Tornadoes and Floods Underscore the Costs of Global Warming
Floods in the Philippines Underscore the Deadly Toll from Climate Change
Hurricane Irene and the Staggering Costs of Climate Change
Extreme Weather Makes a Convincing Case for Climate Change