The document summarizes key points from a presentation on climate change impacts and risks over the next 10-20 years and longer term. It discusses recent record-breaking global temperatures in 2014 and 2015. It also highlights climate-related extremes in the US in recent years including droughts, heavy rainfall events, heat waves, coastal flooding and hurricane activity. The presentation discusses risks of increased drought severity, heavy precipitation events, heat waves, coastal flooding from sea level rise and storm surge, as well as uncertainty around future hurricane and tornado activity. Longer-term threats discussed include potential for megadroughts and accelerated sea level rise along the US East Coast from ice sheet melting. The document emphasizes that climate change impacts will not stabilize and

1. Bob Henson
Weather Underground | San Francisco, CA
bob.henson@weather.com @bhensonweat
her
Climate Change 2015:
Understanding and Responding to
the New Normal
Natural Hazard Mitigation Assoc.
Practitioners Symposium
Broomfield, CO
23 July 2015
http://www.wunderground.com/
wximage/capritaur/1?gallery=Jan Null

2. Let’s look at . . .
Some recent data
The next 10-20
years
Evolving risks
NASA
Longer-term threats
(midcentury and beyond)

3. Climate is
what you expect;
www.extremeinstability.com
weather is
what you get.
—Robert Heinlein,
Time Enough for Love

4. For the planet, 2014 is warmest year on record
(and 2015 looks warmer still)
2014 State of the Climate report—just
releasedhttp://www.ncdc.noaa.gov/bams-state-of-the-climate/2014.php
NOAA/NCEI

5. The “global warming
hiatus” is dead!
For the planet, 2014 is warmest year on record
(and 2015 looks warmer still)
NOAA/NCEI

6. A weird twist . . .
The only large cold spots in 2014:
eastern N. America and central Asia
NOAA/NCEI

7. NOAA/NCEI
A weird twist . . .
Feb. 2015 — even more dramatic

8. A weird twist . . .
NOAA/NCEI

9. A weird twist . . .
NOAA/NCEI

10. Western drought/heat
$2+ billion in 2015 Calif.
impact;
all-time temp records
getting smashed
New Molones Reservoir, CA • May 24, 2015 • Mark Ralston/AFP/Getty Images
2015 thus far: A study in US contrasts

11. Deluge in
the heartland
May is wettest month
on record in TX, OK;
wettest June
in IL, IN, OH
2015 thus far: A study in US contrasts
Western drought/heat
$2+ billion in 2015 Calif.
impact;
all-time temp records
getting smashed
Western drought/heat
$2+ billion in 2015 Calif.
impact;
all-time temp records
getting smashed
Interstate 45, Houston • May 26, 2015 • Aaron M. Sprecher/AFP/Getty Images

12. Brutal winter in
Northeast
Boston paralyzed for
weeks by record snow;
coldest Jan-Mar in NY
state history
2015 thus far: A study in US contrasts
Deluge in
the heartland
May is wettest month
on record in TX, OK;
wettest June
in IL, IN, OH
Western drought/heat
$2+ billion in 2015 Calif.
impact;
all-time temp records
getting smashed
Surface Road, Boston • Feb. 15, 2015 • Scott Eisen, Getty Images

13. One for the record books?
Already at “strong” levels:
models suggest an El Niño event this fall/winter
on par with epic 1982-83 and 1997-98 events,
possibly the strongest on record
ClimateReanalyzer.org • University of Maine
Here comes El Niño

14. The next 10 – 20 years

15. What’s kept eastern N. America cool?
ClimateReanalyzer.org • University of Maine
Loss of Arctic sea ice?
Warmth in tropical Pacific?
Just a random variation?
Research debate is ongoing
Next couple of years will tell us much

16. The great shift in summer Arctic ice
UCAR/Carlye Calvin
Sometime in next several decades, we can expect a summer
with > 90% open water across the Arctic Ocean
Huge implications for wildlife, economy, indigenous peoples,
climate (at least regionally)

17. A new era of
El Niño?
Pacific
Decadal
Oscillation
swinging
toward
positive mode,
which favors
El Niño—
possibly
through
the late 2010s
and 2020s
-PDO+PDO
http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=2923
+PDO+PDO -PDO -PDO

18. Evolving risks

19. Drought: packing more punch
Yosemite Nat’l Park, 2/18/15
Elizabeth Christie
https://twitter.com/NWSHanford/status/568286823719440385
Temperatures soaring to new highs, even
when rainfall drop isn’t unprecedented
Reduced snowpack
Water management challenges
Heightened wildfire risk (conditional)

20. Goosing of the hydrologic cycle
Heaviest one-day precip events are getting
heavier
Higher flash flooding risk (conditional)
Reduced absorption for crops
Purdue University Agricultural Communication photo/Darrin Pack

21. Heat waves
Overall rise in temps leading to hotter summers,
greater heat-wave potential
Nights warming faster than days
Major U.S. progress in safety (e.g., cooling
centers)
What are remaining weak points?
(Hansen et al., PNAS 2012)

22. Coastal flooding
“Sea Level Rise and Nuisance Flood Frequency Changes around the United States”, NOAA Technical Report NOS
CO-OPS 073 (2014)
Gulf and Atlantic coasts are increasingly
vulnerable
Storm surge (hurricanes, winter storms)
“Nuisance” flooding
Development, subsidence, other complications

23. Hurricanes
https://notalotofpeopleknowthat.wordpress.com/2015/05/02/us-major-hurricane-drought-longest-on-record/
Nearly 10 years since our last Cat. 3 U.S. landfall!
How will landfalls evolve, apart from sheer # of
storms?
Has a multidecadal drop in Atlantic hurricanes
begun?

24. Tornadoes
Seasons becoming more variable, with active
clusters separated by quiet periods
Will out-of-season tornadoes
increase?
Is there public value in seasonal
forecasts?
Bob Henson
(Elsner, Climate Dynamics 2015)

25. Longer-term threats

26. Megadrought?
New research reinforces the idea that temperature
rise will be the main factor making droughts worse
How to maintain drought awareness in wet years?
Which crops, trees can best handle wild precip
swings?
In case of megadrought, what’s the Plan B?
(Diffenbaugh et al., PNAS 2015)
Justin Sullivan/Getty Images

27. Sea level rise: One size doesn’t fit all
MSL rise will be especially fast along northeast U.S. coast
Do people realize the added East Coast risk?
Could the W Antarctic Ice Sheet give us a shock?
What’s the multicentury viability of our vulnerable
coasts?
U.S. Coast Guard via Getty Images
(Sallenger et al., Nature Climate Change 2012)

28. Planning for a moving target
Our climate won’t hit a target and stay there!
Variability will continue on all time & space scales,
even as global climate warms/evolves
What’s best tempo/sequence for adaptation
measures?
How do we bring variability into scenarios?
How to convey big-picture confidence/local

29. Thank you!