Future  Projec+ons  

•  Temperature  •  Deep  Ocean  heat  transfer  •  Climate  sensi+vity  •  Tropical  storms  •  Other  variables  

IPCC,  AR5,  Fig.  12.44  

IPCC,  AR5,  Fig.  12.41  

IPCC,  AR5,  Fig.  12.40  

Baker  and  Roe,  2009  

€

R dΔTdt

+ λΔT = ΔF (11.2)

€

ΔT (t) = ΔTeq 1− e−tτ%

& ' (

) * (11.3)

€

τ = R λ

€

ΔTeq = ΔFλ

e-folding time

thermal inertia damping

radiative forcing

Mixed layer-only response

€

ΔT (t) = ΔTeq 1− e−tτ%

& ' (

) * (11.3)

€

τ = R λ

€

ΔTeq = ΔFλ

Greater sensitivity: •  greater ΔT •  slower to final change

3.75 Wm-2

7.5 Wm-2

3.75 Wm-2

2K

4K

2K

Effect of heat exchange between mixed layer and deep ocean

Atmosphere warms

IR

SH LH

Mixed-layer

Deep ocean

+ -

-

- themohaline overturning decreases

Steady State With mixed-layer warming

0.52Wm-2

-1.96Wm-2

1.44Wm-2

- diffusion increases - convection decreases

Net Effect: heat transfer from mixed-layer to deep ocean

advection

Sudden CO2 doubling

Net radiation at TOA = flux into deep ocean

IPCC,  AR5,  Fig.  12.42  

IPCC,  AR5,  Fig.  12.35  

Baker  and  Roe,  2009  

Energy  to  deep-­‐ocean  serves  as  nega+ve  feedback  (0.15)  

Narrower  climate  sensi+vity  (transient)  

Baker  and  Roe,  2009  

Which  feedbacks  dominate  uncertainty  (oceanic  or  atmospheric)?  

Reducing  atm.  uncertainty  is  more  important  

IPCC,  AR5,  Box  12.2,  Fig.  1  

IPCC,  AR5,  Box  12.2,  Fig.  2  

Baker  and  Roe,  2009  

When  will  temperature  reach  a  given  value?  (with  a  ramped  4  Wm-­‐2  forcing)  

Baker  and  Roe,  2009  

How  do  emissions  affect  projec+ons  of  climate  change?  

Climate  Matters  w/  Jim  Gandy  Chief  Meteorologist  WLTX  Columbia  

hWp://www.wltx.com/weather/climate/default.aspx  hWp://www.wltx.com/video/default.aspx?bc+d=610279275001  

Tropical Cyclones and Climate Change

Challenges  in  detec+ng  trends  and  anthropogenic  influence  in  tropical  cyclone  ac+vity  Ø  Large  amplitude  fluctua+ons  in  frequency  and  intensity  Ø  Short  term  records  Ø  Quality  of  record  

Future  projec+on  of  tropical  cyclones  AO  GCMs  resolu+on  too  low,  so  we  need  1.  Reliable  simula+ons  of  climate  variables  influencing  

tropical  storm  ac+vity  and  reliable  sta+s+cal  rela+onships  between  these  variables  and  tropical  cyclone  metrics  

2.  Or  higher  resolu+on  models  capable  of  resolving  more  processes  

Detection and AttributionIntensity  

Poten+al  Intensity  Theory:  Local  ambient  thermodynamic  environment  determines  the  maximum  intensity  that  a  hurricane  can  achieve.          

Indirect  aWribu+on  CO2  à  SSTà  Hurricanes  

1.  Warming  SSTs  due  to  GHG  emissions  

2.  SST  influence  on  tropical  cyclonic  ac+vity  

 

Attribution  Intensity  

Power  Dissipa+on  Index  :    Seasonally  integrated  metric  for  storm  dura+on,  intensity,  frequency  

1.  Atlan+c  TC  power  dissipa+on  and  local  SST  

2.  Atlan+c  TC  power  dissipa+on  and  rela2ve  SST  (Diff  between  local  SST  and  mean  tropical  SST)    

0

3maxPDI V dt

τ≡ ∫

(Swanson,  2008)  

Sta+s+cal  es+ma+on  of  Atlan+c  Hurricane  Ac+vity  from  GCM  projec+ons  of  sea  surface  temperatures    

 

Projections  Intensity  

(Vecchi  et  al.,  2008)  

Detection and Attribution Frequency  

No  significant  trend  detected  in  tropical  cyclones  or  landfalling  hurricanes  (1970-­‐2004)  

Quality  of  Historical  Records    

Mul+decadal  variability  

(Vecchi  and  Knutson,  2008)  

Projections  Frequency  

(Villarini  and  Vecchi,  2012)  

Stat/dyn  downscaling  (obs.  SSTs)  

Regional  modeling  (obs.  SSTs,  nudging)  

100-­‐km  AGCM  (obs.  SSTs)  

50-­‐km  AGCM  (obs.  SSTs)  

(Knutson  et  al.,  2008)  

observed  

10  least-­‐ac+ve  years,  1980-­‐2006   10  most-­‐ac+ve  years,  1980-­‐2006  

Simulated  (control)  

Simulated  (warm  climate)  

Global  TC  ac+vity  change  (2081-­‐2100)  rela+ve  to  2000-­‐2019  

(IPCC  AR5  WG1  Fig.  TS.26  )  

References

•  IPCC,  2013.  Working  Group  I  Contribu+on  To  The  IPCC  Fihh  Assessment  Report  (AR5),  Climate  Change  2013:  The  Physical  Science  Basis.  Drah  Report    

•  IPCC,  2012:  Managing  the  Risks  of  Extreme  Events  and  Disasters  to  Advance  Climate  Change  Adapta+on.  A  Special  Report  of  Working  Groups  I  and  II  of  the  Intergovernmental  Panel  on  Climate  Change  [Field,  C.B.,  V.  Barros,  T.F.  Stocker,  D.  Qin,  D.J.  Dokken,  K.L.  Ebi,  M.D.  Mastrandrea,  K.J.  Mach,  G.-­‐K.  PlaWner,  S.K.  Allen,  M.  Tignor,  and  P.M.  Midgley  (eds.)].  Cambridge  University  Press,  Cambridge,  UK,  and  New  York,  NY,  USA,  582  pp.  

•  Knutson,  T.  et  al.  2010.  Tropical  cyclones  and  Climate  Change.  Nature  Geoscience.  3:157-­‐163  •  Swanson,  K.  2008.  Nonlocality  of  Atlan+c  tropical  cyclone  intensi+es.  Geochemistry  

Geophysics  Geosystems.  9  •  Vecchi,  G.,  Knutson,T.  2008.  On  es+mates  of  historical  North  Atlan+c  tropical  cyclone  ac+vity.  

Journal  of  Climate.  21:3580-­‐3600  •  Vecchi,  G.,  Swanson,  K.,Soden,  B.  2008.  Whither  hurricane  ac+vity.  Science.  322:687-­‐689  •  Villarini,  G.  and  Vecchi,  G.  2012.  Projected  increases  in  North  Atlan+c  tropical  cyclone  

intensity  from  CMIP5  Models.