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Global  Environmental  Change  

What  are  things  to  watch  and  how  will  vegeta7on  change  

Planet  is  warming  

Solar  ac7vity  and  global  temperatures  are  not  in  sink  

Issue of global origin Basis  of  climate  change  

Basis  of  climate  change  

•  Human  changes  that  increase  CO2  into  the  atmosphere  or  other  greenhouse  gasses.  – Burning  of  fossil  fuels  (net  gain)  – Burning  of  vegeta7on  (global  issue)  – Disturbance  of  natural  communi7es  (major  increases  in  decomposi7on  =  net  CO2  increase)  

•  Greenhouse  gasses  increase  global  average  temperatures  

Fossil  Fuel  Emission

 (Gigaton

s  C/yr)   Increases  greenhouse  gasses  

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10,000 year record indicates CO2 increases associated with recent period.

A 400,000 year record suggests variation in CO2, but less than current levels.

LAND USE CHANGES, e.g., cutting down forests for agriculture, paving over vegetation, converting agriculture to suburbs or towns, greatly increase CO2 emissions. Anyplace with population growth or other development pressures (like forestry for other places) accelerate emissions.

Consider the balance between production and decomposition following disturbances.

Greenhouse  Effect:      How  does  it  Work?  

•  Energy  arrives  from  the  sun  at  high  energy  wavelengths  (UV,  light)  and  leaves  at  lower  energy  wavelengths  (IR  heat).  

•  CO2  is  ‘clear’  to  higher  energy  wavelengths  but  opaque  in  the  IR;  heat  is  trapped  in  the  atmosphere  

Greenhouse  Effect   Overwarming  

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These graphs show the differences for years since 1850 compared to the 1961-1990 average

Planet  is  warming  

Copenhagen  Summary  Report  2009  

Changes  global  average  air  temperature  (rela7ve  to  1990)  

-­‐IPCC  projec7ons  

Days  and  nights  are  warming  

Cool colors- decrease in frequency

Warm colors- increase in frequency

See bar graphs

For example, Marmots are emerging from hibernation on average 23 days earlier than 23 years ago. This coincides with an increase in average May temperatures of about 1.8°F (1°C) over the same time period.

Inouye  et  al.  2000.  PNAS  USA  97:  1630-­‐1633.  

Animal behavior and plant ranges are shifting.

Real  problem  is  Phenology  

•  Disjunc7ons  in  the  7ming  of  plant  and  animal  ac7vity  (pollina7on  and  dispersal  for  plants;  food  resources  for  animals)  

Temperature  increases  on  plant  communi7es  

Recall that plant enzymes, like those in photosynthesis, operate optimally in a limited range of temperatures. At either extreme, rates of respiration can exceed photosynthesis.

Shifts to warmer temperatures will cause major shifts in plant communities.

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Tropical  Trees  are  slowing  in  growth  rates  

Varia7on  in  Annual  Growth  in  Tropical  Trees  Measured  by  Diameter  Growth  of  trunks.  

Problem?    The  lack  of  growth  is  all  recent…  

…and  it  correlates  directly  with  increasing  CO2  flux  (addi7ons  to  atmosphere)  

Tropical  Tree  Growth  is  restrained  by  higher  daily  

minimum  temperature  (night  7me).  

Tropics:    Not  going  to  be  a  carbon  sink  

Huge  increases  in  CO2  addi7ons  to  the  atmosphere  under  both  ‘baseline’  (current  rates)  or  ‘reduced  PS’  scenarios.  

Note that the tropics were hoped to be a major carbon sink, but these data force a re-evaluation from sink to neutral, or even a carbon source if warming trends continue.

Figure 3 | Changes in the Qori Kalis Glacier, Quelccaya Ice Cap, Peru, between 1978 (a) and 2002 (b). Glacier retreat during this time was 1,100m (L. Thompson, personal communication). Photographs courtesy of L. Thompson.

Glaciers are melting.

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"On the left is a photograph of Muir Glacier taken on August 13, 1941, by glaciologist William O. Field; on the right, a photograph taken from the same vantage on August 31, 2004, by geologist Bruce F. Molnia of the United States Geological Survey (USGS)." Image credit: National Snow and Ice Data Center,

W. O. Field, B. F. Molnia.

Greenland’s ice sheet melts more and more each year.

Melt water flows into a large moulin in the Greenland ice sheet. Image credit: Roger J. Braithwaite, The University of Manchester, UK. Image Source: NASA.

Permafrost covers a massive amount of the northern hemisphere. Decomposition from thawed areas will release large amounts of ‘stored’ organic CO2.

Projected loss of both permafrost and sea ice in the arctic regions.

•  Permafrost thawing. Permafrost thawing is causing the ground to subside 16-33 ft (4.9-10 m) in parts of interior Alaska. The permafrost surface has warmed by about 3.5oF (1.9oC) since the 1960's.

Osterkamp  and  Romanovsky.  1998.  Permafrost  and  Periglacial  Processes  9:  87-­‐89.  

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Average October arctic sea ice coverage as observed by satellites between 1979 and 2010. Image credit: National Snow and Ice Data Center.

What  normally  happens  in  the  arc7c?  Albedo  effects    

Snow  reflect  solar  heat,  keeping  the  earth  rela7vely  cool.  

As  snow  melts  sooner  with  global  warming,  shrubs  and  trees  invade  north,  crea7ng  a  posi7ve  feedback  system  of  more  rapid  warming  

Barnett et al. 2005. Nature 438: 303-309.

Posi7ve  feedback  results  from  shif  from  reflec7ve  snow,  to  absorp7ve  shrubs  and  trees.    Anything  that  decreases  

albedo  increases  rate  of  warming.  

Chapin et al. 2005. Science 310:657-660.

Oceans  are  warming   Marine  systems  impacted  as  well  Warmer temperatures off the coast of California have resulted in declining abundance of fish and lower productivity apart from anything else happening in the system.

The proportion of cold water species is declining, and warmer water species are increasing

Dead zones increase in size?

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Sea-­‐level  is  rising  rapidly  

-­‐Sea  level  has  recently  been  rising  at  a  rate  of  23  cm/century  and  is  predicted  to  increase  

-­‐The  higher  rates  shown  are  areas  also  subsiding.  -­‐The  low  Alaskan  rate  is  because  land  is  s7ll  rising  since  last  glacial  epoch.  

Recent  data  from  Greenland  indicates  these  may  be  underes7mates.  

Sea  level  trends  (U.S.)  

Land rising faster than the ocean

Net increase in Sea Level

Sea  level  is  rising  at  increased  rates  From  1.1-­‐>3.2  mm/yr;  projec7ons  4-­‐17  mm/yr  

Sources  of  sea  level  change  

Sources of sea level rise and their contributions in mm per year for the periods 1961-2003 and 1993-2003 from the IPCC 2007 assessment. Image credit: modified from Bindoff et al., 2007 (IPCC).

NOAA  2012  Sea  Level  Rise  Es7mates   NOAA  2012  Sea  Level  Rise  Es7mates  

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California  

California  Summary  of  model  predic7ons  

•  Warmer  temperatures  mean  earlier  spring  meltoff  in  the  mountains  

•  Spring  pulse  of  river  flow  shifs  earlier,  summer  flows  decline  considerably  

•  Summer  deficits  of  available  water,  reservoirs  insufficient  

•  Terrestrial  areas  dry  out  more,  increases  in  fire  frequency,  shifs  in  vegeta7on  types  

•  More  varia7on  in  weather,  more  violent  winter  storms,  drier  springs  

•  Along  with  sea  level  rise,  salinity  increases  through  estuaries    

California  summer  temperatures  

The extent of temperature rise isn’t known yet, as it depends on whether we bring emissions of greenhouse gasses down or not.

6 global climate models for each of 4 different historic and future scenarios.

The suite of models shows that northern California will increase in temperature.

The models are ambivalent about precipitation, most indicating no net change with some showing large increases or decreases. More recent models suggest less precipitation in northern California and the Sierra

Same data as previous slide shown in a different manner.

Each line represents a frequency distribution of the various models and scenarios for different years.

Net interpretation: temperature increases, precipitation doesn’t change much.

Contour diagrams of both shifts in temperature and precipitation predicted by the suite of model runs.

Next 50 yr, N. California gets warmer, same total precipitation.

Almost 100 yr from now, much warmer and precipitation may decrease.

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Expect increased temperatures to have direct impacts on humans, as well as on natural systems.

Actual projections of changes to the Sierra Nevada Snowpack are fairly intimidating, even under a reduced emissions scenario.

Distributions of annual streamflow amounts and median-flow dates (i.e., date by which half of a year’s flow is past) in the North Fork American River, in response to 20,000 resampled climate-change realizations.

Streamflow will shift to 1) net lower annual flows, 2) earlier in the season.

Rainfall, as a fraction of total precipitation in mountains, increases through time.

Reinforces the shift of snowmelt to earlier and earlier.

Impact  of  shifs  in  snow  melt  and  in  overall  snow  cover  

•  Decreased  summer  flows  will  intensify  compe7ng  demands  for  water  to  meet  needs  of  agriculture,  industry  and  urban  areas  

•  The  health  of  California’s  aqua7c  and  streamside  ecosystems  will  be  at  risk  

•  Will  shif  flooding  risks  earlier  into  the  winters,  poten7ally  coinciding  with  major  rainfall  events  

•  Cause  major  changes  in  what  crops  will  be  possible,  and  perennial  crops  like  fruit,  nuts  and  grapes  are  most  vulnerable  because  it  takes  so  long  to  replace  them  

Fire  regimes  in  California  

•  Changes  in  hydrology  also  mean  greater  water  stress  in  the  summer  growing  seasons  due  to  loss  of  water  storage  (earlier  snowmelt,  greater  rainfall  propor7on,  higher  temperatures)  

•  Greater  water  stress  will  decrease  ecosystem  produc7vity  and  increase  fire  frequencies  in  some  vegeta7on  types  

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Annual area burned is predicted to increase regardless of model parameters used.

The red line indicates a 10% increase in annual area burned. Remember this means it will take fewer years to burn what currently burns in 100 years.

Shifs  in  vegeta7on  

Not only will changes in fire regime affect plant communities, but simple shifts in temperature will do that by itself.

Plants are limited both by absolute extremes, and also by the range of temperatures in which they can survive.

There will be major shifts in vegetation, some increasing, some declining.

-Grasslands expand into chaparral -Forests lose to shrublands -Mixed forests eliminate high elevation forests -Alpine decreases

Grasslands and Mixed Evergreen Forest are the types that increase greatly in the future .

Sea  Level  Rise  and  Levees  

1100 miles of levees; a one foot rise in sea level (~30 cm) would transform the current ‘high tide peak’ from an event that occurs once every 100 years, to one that will average every 10 years

CO2

Higher Temperatures Higher Resources

Productivity (C3)

Reduced precipitation Reduced snowpack Earlier snowmelt Lower river & streamflows Higher evapotranspiration

Sea Level Rise

Salinity increases in estuaries

+ + -

-

-

Climate  change  and  7dal  wetlands  

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Climate  change  and  7dal  wetlands  

•  Uncertain  about  net  impacts  of  CO2,  increased  temperatures,  etc  

•  Sure  about  the  impacts  of  rising  sea  level  in  rela7on  to  inunda7on  and  salinity  

Subsidence  &  compac7on  

Sea  Level  Rise  

Rela7ve  Wetland  surface  eleva7on  

Processes  contribu7ng  to  eleva7on  decline  

Sediment  supply  

Plant  organic  mamer  

Rela7ve  Wetland  surface  eleva7on  

Processes  contribu7ng  to  eleva7on  increase  

Potential changes in SF-Bay Delta wetlands.

Sed, SLR Sed, SLR

Sed, SLR Sed, SLR

Stralberg et al. 2011 PLoS One

Potential changes in SF-Bay Delta wetlands.

Schile et al. in press PLoS One

SLR Sed

SLR Sed

Schile et al. in press PLoS One

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San Francisco Bay Area with a 1 m rise in sea level

Salinity (ppt)

0 5 10 15 20 25 30 35

Current  Summer    

Salini7es  

Projected  Summer  

Salini7es  in  2060  

Figure from Noah Knowles

Projected  Salinity  Changes  Cri7cal    

Alternate  scenarios  of  climate  change  

What  can  change  these  predicted  scenarios?  Deflected  Gulf  Stream?  

•  If  Gulf  Stream  is  deflected  south,  then  we  will  cool  the  north  temperate  zone,  at  least  temporarily.  

•  New  data  that  the  Gulf  Steam  is  slowing  down  

The North Atlantic heat conveyor. Most warm waters in the upper ocean circulate clockwise in a giant horizontal swirl in the subtropics, but some flow farther north and cross the Greenland –Scotland Ridge (GSR). This branch warms the northern North Atlantic and Europe, and keeps most of the Nordic Seas free of ice. Here the water sinks (indicated by the star) and flows back southwards at depth, mostly down the western edge of the Atlantic basin. According to recent data, the northern branch is weakening and the latter strengthening. Bryden et al. 2005 Nature

438, 655–657

weakening

strengthening

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Summary-­‐1  

•  CO2  and  other  greenhouse  gasses  are  being  added  to  the  atmosphere  at  increasing  rates  

•  Industry,  cars,  etc  are  definitely  large  sources  of  CO2,  but  also  land-­‐use  changes  increasing  decomposi7on  

•  Climate  models  incorpora7ng  more  greenhouse  gasses  such  as  CO2  indicate  global  warming,  especially  in  the  higher  la7tudes  (more  as  warmer  winters  than  super-­‐hot  summers)  

Summary-­‐2  

•  Climate  models  also  indicate  great  fluctua7ons  (storm  events,  droughts  to  floods,  more  hurricanes,  etc)  

•  California?    Loss  of  snowcover,  earlier  water  flow  –  more  flooding  in  spring,  drier  summers,  spread  of  salt  marshes  at  the  expense  of  brackish  and  freshwater  systems  or  their  loss,  increased  fire  frequency,  shifs  in  vegeta7on  dominance  

•  Trend  to  warmer  climates  may  be  offset  by  a  loss  of  the  northern  branch  of  the  Gulf  Stream,  poten7ally  bringing  back  a  “limle  ice  age”;  or  increases  in  volcanic  erup7ons  might  aid  as  well.  

Most of these predictions are based on climate models. What is the confidence scientists have in these models and their predictions?

This chart shows the range for different issues.

Confidence  in  these  Predic7ons?   Final  Comments  

Summary?  •  None  possible  •  Go  into  the  world  with  your  eyes  opened  •  Enjoy  climate  change  and  the  great  storms  we  will  have  from  now  on-­‐  you’ll  be  able  to  amaze  your  friends  by  predic7ng  how  vegeta7on  around  you  will  change  

•  Stun  your  family  by  charng  about  vasicentric  tracheids  or  mumering  “con7ngent  mass-­‐effects  metacommunity”  at  the  holiday  dinner  table  

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Final on Saturday

•  Saturday, 21 December – 10:45-1:15

– 4 questions selected from a larger number

– Bring a bluebook (greenbook)