An overview of the scientific evidence that climate change is occurring, and what was normal in the past is not going to be normal for the future. Recent extreme-weather events -- snowstorms, last summer's derecho, and two severe hurricanes in the space of just over a year, are harbingers of more to come. Because the future will be different, we must use future-based modeling rather than historical data to prepare.

1. Climate Change and Extreme Weather:
A New Normal?
Anthony J. Broccoli
Director, Climate and Environmental Change Initiative
Department of Environmental Sciences
Rutgers University
“Rebuilding a Resilient New Jersey Shore”
Monmouth University
December 7, 2012

2. Mantoloking Ortley Beach

3. “Extreme weather is the new normal. In the past two years, we have
had two storms, each with the odds of a 100-year occurrence.”
- Governor Andrew Cuomo
“Our climate is changing. And while the increase in extreme weather
we have experienced in New York City and around the world may or
may not be the result of it, the risk that it might be — given this
week’s devastation — should compel all elected leaders to take
immediate action.”
- Mayor Michael Bloomberg

4. Four Questions
• What do we mean by “normal” climate?
• Is there a new normal?
• If there is a new normal, were Sandy and other
recent extremes harbingers of future events?
• How can we prepare for future weather and
climate impacts?

5. What do we mean by “normal” climate?
• We use the term “normal” to describe the expected range of
conditions, including averages and extremes, at a location.
• This definition of normal arises from the concept of stationarity.
• “Stationarity is the assumption that the future will be similar to
the past, in a statistical sense.” (Milly 2007, Ground Water News
and Views)
• In a stationary climate, the weather events that occur would be
drawn from an underlying probability density function with
properties that could be determined from the observational
record (for example, a “100-year storm”).

6. Is there a new normal?

7. Climate Change 101: The Basics
• Combustion of fossil fuels (coal, petroleum, natural
gas) emits carbon dioxide into the atmosphere
(currently about 9 billion tons of carbon per year).
• Slightly less than half of the carbon dioxide remains in
the atmosphere; most of the remainder goes into the
ocean (causing ocean acidification).
• Increasing carbon dioxide heats the earth; global
temperatures have risen by 1-1.5°F during the past
century.
• Increasing temperatures also cause other changes in
climate and sea level.

8. Climate change alters the probability of
extreme events
Probability of summer
temperature over all
Northern Hemisphere
land grid boxes (using
1951-1980 baseline)
[Hansen et al. 2012, PNAS]

9. New Jersey summer temperature trends
[Source: National Climatic Data Center]

10. Were Sandy and other recent extremes
harbingers of future events?
“Boxing Day
Snowstorm”
Irene

11. Millstone, NJ
New Brunswick, NJ
Manville, NJ
Paterson, NJ

12. October 2011 Snowstorm

13. Hurricane/Superstorm Sandy
Sandy All previous tropical cyclones passing
within 50 miles of Atlantic City

15. Storm surge at The Battery

17. What the science tells us…
• We do not know if tropical cyclone activity
(i.e., intensity, frequency, duration) has changed systematically in the
past. In the future, tropical cyclones will probably increase in strength but
their number will either decrease or remain essentially unchanged.
• We do not know if severe thunderstorms and tornadoes have become
more frequent (because observational methods have improved) and future
trends are uncertain.
• Many areas have experienced upward trends in the number of heavy
precipitation events and it is likely that such trends will continue
throughout the 21st century.
• Record high temperatures and heat waves have been occurring more
frequently and they are expected to increase further during the 21st
century.
• The ongoing rise in sea level has raised the baseline for coastal flooding
from storm surge and the rate of sea level rise will likely accelerate during
the remainder of the 21st century.

18. Sea level trends along NJ coast
16 inches in 100 years
Projection for 2050: 11-25 inches (best estimate of 16”)
Projection for 2100: 27-67 inches (best estimate of 43”)
[Source: R. Kopp and K. Miller, Rutgers University, paper in prep.]

19. Historic water levels at Sandy Hook
• >13.2 FT — October 29, 2012 (Sandy)
• 10.1 FT — September 12, 1960 (Hurricane Donna) / December 11, 1992.
• 9.8 FT — August 28, 2011 (Hurricane Irene).
• 9.7 FT — November 7, 1953.
• 9.4 FT — September 14, 1944 (Hurricane) / March 6, 1962.
• 9.0 FT — November 25, 1950.
• 8.9 FT — January 23, 1966.
• 8.8 FT — November 12, 1968.
• 8.7 FT — MAJOR TIDAL FLOODING BEGINS.
• March 29, 1984 / March 13, 1993.
• 8.6 FT — September 27, 1985 (Hurricane Gloria) / January 2, 1987 / October 31, 1991.
• 8.5 FT — April 13, 1961.
• 8.3 FT — February 19, 1972 / March 19, 1996 / March 13, 2010.
• 8.2 FT — October 18, 2009.
• 8.1 FT — January 31, 2006 / April 16, 2007.
• 8.0 FT — October 14, 1955 / December 26, 1969 / December 2, 1974 / April 16, 2011.
• 7.9 FT — August 31, 1954 (Hurricane Carol) / December 22, 1972 / October 25, 1980 / February 24, 1998 /
December 25, 2002 / November 14, 2009.
• 7.8 FT — October 14, 1977 / November 8, 1977 / March 3, 1994 / December 20, 1995 / January 29, 1998 /
March 30, 2010.
• 7.7 FT — MODERATE TIDAL FLOODING BEGINS.
• March 20, 1958 / October 22, 1961 / November 10, 1962 / December 25, 1978 / December 3, 1986 /
January 4, 1994 / December 13, 1996 / November 14, 1997 / January 3, 2003 / January 3, 2006 / February
12, 2006 / October 7, 2006 / May 12, 2008 / December 12, 2008 / May 17, 2011.
• 6.7 FT — MINOR TIDAL FLOODING BEGINS

20. The future will not be the same as the past
• “We never had floods like this before. We made
preparations but it didn’t do any good…”
• “There was no reason for us to think that the kind of
flooding that we actually experienced would happen there.”
• “We had flooding in areas we never had flooding before.”
• “...we've never had flooding before…The house has been in
the family since it was built in 1964 and there's never been
a problem with weather...ever.”
• “They thought they'd be safe because they'd never had
flooding before.”

21. How can we prepare for future
weather and climate impacts?
• Recognize that the past is not an adequate guide to what will
happen in the future (finite sample size, changing climate).
• Use information from climate model projections, with careful
interpretation, to develop an understanding of the effects of a
changing climate baseline.
• Focus on aspects of climate change that we understand with high
confidence (such as sea level rise) rather than those that are
more uncertain (such as changes in storm frequency/intensity).
• Develop improved methods for making projections of the effects
of climate change on high impact weather events.

22. Example: Estimating future flood return levels
Black curve is for present climate; red and blue curves depict estimated flood return
levels for period 2081-2100 under IPCC A1B emissions scenario. (Lin et al. 2012)

23. Example: Projecting changes in severe weather
Severe thunderstorms and
tornadoes occur where moisture
is abundant , the atmosphere is
unstable, and vertical wind shear
is large.
Convective available potential
energy and specific humidity
increase
Vertical wind shear decreases
Net result: Increase in severe
thunderstorm environment days
Source: Trapp et al. (2007, PNAS)

24. Four Questions
• What do we mean by “normal” climate?
Implicit assumption: Climate is quasi-stationary
• Is there a new normal?
Stationarity is dead.
• If there is a new normal, were Sandy and other
recent extremes harbingers of future events?
Yes for some types of extremes; uncertain for
others.
• How can we prepare for future weather and
climate impacts?
Use best available science.