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John P. HoldrenTeresa & John Heinz Professor of Environmental Policy

Kennedy School of Government and

Professor of Earth & Planetary Sciences HARVARD UNIVERSITY

President Emeritus and Senior Advisor to the President WOODS HOLE RESEARCH CENTER

Former Chief Science Advisor to President Obama (Jan 2009- Jan 2017)

Presentation for the C2ES Business Environmental Leadership Council

Washington DC / 16 November 2018

Implications of Recent Insights From Climate Science

Science Insights Underscored by Recent Observations

“Science is true whether or not you believe in it.”

Neil deGrasse Tyson

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Modest increase in average T leads to very large change in heat extremes

Thus, in a warmer climate, high-T extremes that previously had probability of occurrence near zero occur with some regularity. This disproportionate impact at the extremes applies to any normally distributed climate-related variable.

Science insights underscored by recent observations

All-time high-temperature records set in 2017-18• Iran 129°F June 2017• Pakistan 128°F May 2017• Africa 124°F July 2018• Spain 117°F July 2017• Chile 113°F Jan 2017• Los Angeles 111°F July 2018• Argentina 110°F Jan 2017• Armenia 108°F July 2018• Shanghai 106°F July 2017• San Francisco 106°F Sept 2017• Denver 105°F June 2018• Hong Kong 102°F Aug 2017• Scotland 92°F June 2018

Science insights underscored by recent observations

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Climate change exacerbates drought

• Altered atmospheric circulation patterns also play a role.

• Higher temperatures = bigger losses to evaporation.

• More of the rain falling in extreme events = more loss to flood runoff, less moisture soaking into soil.

• Mountains get more rain, less snow, yielding more runoff in winter and leaving less for summer.

• Earlier spring snowmelt also leaves less runoff for summer.

Science insights underscored by recent observations

Warming worsens wildfires• US fire season ≥3 months longer

than 40 years ago.• Average fire much bigger & hotter

than before. • Nine of 10 biggest U.S. wildfires

took place since 2004 (the other in 1997). in

• Five these were in Alaska, where now even the tundra burns.

• Smoke from today’s big fires impacts impactshealth 1000s of miles away.

Aniak, AK, June 2015

Science insights underscored by recent observations

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EPA 2016

A warmer atmosphere holds more water, so more can (and does) come down at one time.

Warming causes bigger torrential downpoursScience insights underscored by recent observations

East Baton Rouge, LA, August 2016: Up to 20 inches of rain in 3 days

Bigger downpours mean more floods“Hundred-year” floods now occur once a decade or more in many places.

Hurricane Harvey brought >50 inches of rain over 5 days to parts of Texas in August 2017.

Science insights underscored by recent observations

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Hansen 2017

Thermal expansion & melting land ice lift sea level

Rise continues to accelerate; post-2010 rate is actually 5.5 mm/yr!

Science insights underscored by recent observations

EPA 2016

Rising sea level is causing more coastal inundationScience insights underscored by recent observations

EPA 2016

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• Tropical cyclones get their energy from the warm surface layer of the ocean (which is getting warmer and deeper under climate change). This means more energy is available for evaporating water from the ocean surface. See figure.

• When the water vapor condenses, it heats the atmosphere. The heated air rises, which lowers pressure at the surface.

• That causes air from surrounding areas to flow inward; the spiral pattern results from Coriolis forces.

• More ocean energy stronger cyclone; and deeper ocean warm layer means waves churn up less cold water to limit storm’s power.

Warming causes more-devastating cyclones

In the region that spawned Cyclone Haiyan, the Tropical Cyclone Heat Potential had gone up 20% since 1990.

• Many factors affect the formation and tracks of these storms, but, all else equal, a given cyclone will be more powerful in the presence of a warmer ocean with a deeper warm layer than it would be otherwise. And the higher local sea level is, the worse the storm surge from any given cyclone will be.

Science insights underscored by recent observations

Observed strengthening of tropical storms• 10/12: Sandy, largest ever in Atlantic• 11/13: Haiyan, strongest in N Pacific• 10/15: Patricia, strongest worldwide• 10/15: Chapala, strongest to strike Yemen• 02/16: Winston, strongest in S Pacific• 04/16: Fantala, strongest in Indian Ocean• 10/17: Ophelia, strongest in E Atlantic

Sandy

Winston

Science insights underscored by recent observations

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Climate disruption impacts valued species

“As of February 2017, the ongoing global coral bleaching event continues to be the longest and most widespread ever recorded.”

https://coralreefwatch.noaa.gov/satellite/analyses_guidance/global_coral_bleaching_2014-17_status.php

Jarvis Reef, South Pacific (courtesy WHOI)

Science insights underscored by recent observations

Observed impacts on valued species (continued)

Shifting patterns in Pacific climate, West Coast salmon survival rates, and increased volatility in ecosystem services

Science insights underscored by recent observations

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What the Science Indicates Is Coming

“Prediction is difficult, especially about the future.”Neils Bohr

Temperatures will continue to riseBut how much they rise depends strongly on emissions.

NCA4 Science Report, 2017

What the science indicates is coming

Momentum in the climate system means T continues to go up even after atmospheric conditions stabilize. And sea level continues to go up even after T stabilizes.

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Absent big, fast emissions cuts, we can expect…• Record heat waves as “the new normal”• Far more torrential downpours & flooding• Large expansion in area burned by wildfires• Destruction of most of the world’s coral reefs• Wider disruption of marine food webs & fisheries• Big increases in frequency & intensity of droughts• More Cat 3-5 hurricanes/typhoons making landfall• More sickness & death from heat stress, tropical diseases• Falling agricultural yields for maize, wheat, rice, soybeans…• Sea-level rise reaching ≥0.5 m by 2050, ≥1 m by 2100, 6-10 m

eventually• And, as a result, much bigger flows of environmental refugees

What the science indicates is coming

Implications for Action

“If you don’t change direction, you’ll end up where you’re heading.”

Lao Tzu

“Between fatalism and complacency lies urgency.”

Jake Sullivan, National Security Advisorto Vice President Biden

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The October 2018 IPCC report on 1.5ºC vs. 2.0ºC should be a wake-up call for the complacent• It expresses in plain language, with the imprimatur of the

IPCC, what virtually all climate scientists looking at the whole picture already knew:

o Today’s 1ºC is already well past “dangerous”.

o 1.5ºC will be much worse, and we could be there by 2030.

o 2ºC will be much worse still (impacts don’t scale linearly)

• It calls into serious question whether sustainable prosperity can be achieved at all in a 2C world.

• If you already thought 2C was too ambitious a target to be achieved, you’d best hope that turns out to wrong—and work to make it wrong.

Implications for action

The wake-up call (continued)

• The new IPCC report did not look at the consequences of global-avg T increases of 3-4ºC; it had a narrower mandate. But those temperatures are the most likely result of current trends in technological and policy innovation.

• It’s clear from this latest IPCC look at 2ºC, though, as well as from earlier IPCC and many other studies that have considered temperature increases of 3-4ºC, that these higher figures portend climate catastrophe…o a world changed beyond all human experience

o unlivable over much of the land surface in the hottest months

o wracked by storms more powerful than the worst of today’s

o its former coastal cities gone under 6-10 m of sea-level rise

o the productivity of its farms, forests, & fisheries shriveled

Implications for action

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Emissions pathways & T probabilities

Fawcett et al., SCIENCE, December 4, 2015

Avoiding catastrophe requires deep cuts quicklyImplications for action

“Low Policy” case gives ~35% chance of T>4C by 2100.

“Paris Increased Ambition” case gives only ~30% chance of T<2C by 2100.

• A global carbon tax starting soon and escalating from around $30/tCO2e initially to at least $100/tCO2e by 2030, collected by national governments and rebated on a per-capita basis.

This would incentivize using best available low- and no-emission technologies now and investing in RD&D to get better ones.

• A massive program of technological innovation on clean energy and energy efficiency, advanced through partnerships among government, industry, & universities, and including…

o CO2 capture & sequestration for fossil & biomass power plants

o Sustainable biomass production for power plants & aviation fuel

o Cheaper wind & solar power and better electricity storage

o Innovation to make nuclear-energy expansion safe & affordable

o Pursuit of practical fusion power

Implications for action

I believe having any chance of ∆T<2ºC will require…

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What we need (concluded)

• A similarly massive set of public-private-university partnerships focused on developing & implementing adaptation measures to limit the harm from the changes in climate that can no longer be prevented.

* * * *

The political will to get all this done could materialize faster than many think, as the combination of

rapidly increasing damages from climate change

and

declining costs of remedial action (as a result of innovation)

makes ever clearer that action is much cheaper than inaction.

Implications for action

Thank you!