global climate change: what controversies? bryan c. weare atmospheric science program university of...
Post on 21-Dec-2015
217 views
TRANSCRIPT
Global Climate Change: What Controversies?Bryan C. Weare
Atmospheric Science Program University of California, Davis
One of the most important aspects of climate change for
California is the impact on Snow Water Storage
Less snow, more rain in winter means:
1. More flooding in winter
2. Less water in reservoirs in summer for agriculture and cities
During the past 50 years peak spring stream flow has gotten earlier in the
season
CHANGES IN SNOWMELT RUNOFF TIMINGIN WESTERN NORTH AMERICA UNDER A ‘BUSINESS AS USUAL’CLIMATE CHANGE SCENARIOIRIS T. STEWART1, DANIEL R. CAYAN1, 2 and MICHAEL D. DETTINGER
More Rain and/or Earlier Melting Snow
October December April June
100
50
0
River Flow
Human Climate Forcing ParametersCarbon Dioxide- increases primarily
from fossil fuel burning, deforestation
Methane- increases primarily from
intensive agriculture, poor natural gas
production practices
Nitrous Oxide- increases primarily
from vehicles, agriculture
Sulfur Aerosols (dust)- changes
primarily from volcanoes, fossil fuel
(coal) burning
Putting it All TogetherPutting it All Together
Climate models often Climate models often test their skill by test their skill by hind hind castingcasting observed observed climate from 1860 to climate from 1860 to the present.the present.
As the model As the model sophistication sophistication increases to include increases to include greenhouse gasses, greenhouse gasses, aerosols, and changes aerosols, and changes in solar radiation the in solar radiation the model has improved model has improved prediction.prediction.
“The message for the general public should be that this is a real problem, that climate change is happening.
It's projected to occur at a rate in the future that's unlike anything seen in the last 10,000 years, and that rate is likely therefore to be disruptive.”
Kevin Trenberth, Director Climate Division National Center for Atmospheric Research
Other Indicators of Global Climate Change
As lower atmosphere temperatures rise, the temperatures in the stratosphere fall. This is in agreement with basic theories of global warming
Stratospheric Temperature
Lower Atmospheric Temperature
Land Use Changes May Also be Influencing Climate
Urban and Irrigated Crops Have Often Replace Grasslands. This influence can be estimated using a
regional model.
Upward trends are strongest for the minimum temperatures in the Valley
Might this be related to increased irrigation?
50403020100-10-20-30-40-50
0.10.080.060.040.020-0.02-0.04-0.06-0.08-0.1
100806040200-20-40-60-80-100
f : 1996-1901q2 % change
50403020100-10-20-30-40-50
0.5 ms-1
a : 1996-1901Tmax
b : No_Irrig-1901Tmax
d : 1996-1901Soil Moisture
e : 1996-1901Winds; SnowWater % change
c: 1996-1901LH
50403020100-10-20-30-40-50
0.10.080.060.040.020-0.02-0.04-0.06-0.08-0.1
100806040200-20-40-60-80-100
f : 1996-1901q2 % change
50403020100-10-20-30-40-50
0.5 ms-1
a : 1996-1901Tmax
b : No_Irrig-1901Tmax
d : 1996-1901Soil Moisture
e : 1996-1901Winds; SnowWater % change
c: 1996-1901LH
How Global Temperature Changes are Estimated
Local Observation at time t, T’=T-
Tmean
Average all “good” T’ s over a region
Average T’ s over all regions of the globe
A point on the curve at t
Changes in Frequencies of Wet (top) and Dry (bottom) Spells: 1901 to 1998
More Wet Periods
Constant or Fewer Dry Periods