ONLINE RESOURCE 1
Projection of Climate Variables
Downscaled climate projections from the GFDL (GFDL‐Bias Corrected Constructed Analog [BCCA])
model under the two IPCC emissions scenarios, A2 and B1, consist of two parts, monthly climate
projections for 1950-2009 and daily climate projections for 2010-2050. While the historic climate
‘projections’ were used to gain sight about how closely these ‘projections’ trace the actual climate
patterns, only future projections for 2010-2050 were used.
Comparing Projection Model Results to Historical Data
Figures 1 and 2 provide winter (December, January and February) and summer (June, July and August)
month average temperatures for historical projections under B1 and A2 and actual temperatures for 19502009. Table 1 provides the summary statistics for both summer and winter averages for historical
projections and actual temperatures. For the historical period considered here, there exist little differences
between the projected temperatures under B1 and A2. These projections closely follow the path of actual
temperatures-- as shown in table 1, the projections of annual average temperatures were slightly higher
than the actual annual average temperature, only by about 0.278 oC, which is less than 1% of the actual
temperature. Note that our comparison between projections and realized climate does not extend to
climate indices such as degree days and chill hours due to the lack of information on our historical
projections (only the monthly projections were available publicly for the historical period).
Comparison of Summer temperatures between projections
under B1 and A2 and actual temperatures (oC)
26
24
22
20
B1 Summer Avg
A2 Summer Avg
2008
2006
2004
2002
2000
1998
1996
1994
1992
1990
1988
1986
1984
1982
1980
1978
1976
1974
1972
1970
1968
1966
1964
1962
1960
1958
1956
1954
1952
1950
18
actual Summer Avg
Fig. 1 Historical summer (June 1-Aug 31) average temperatures produced by using GFDL monthly
projections (B1 and A2) and using actual daily temperatures for the period of 1950-2009. Up to 2000,
historical projections under B1 and A2 are the same (the red line also represents the blue line)
Comparison of winter temperatures between projections under B1
and A2 and actual temperatures (oC)
15.00
10.00
5.00
2008
2006
2004
Actual Winter Avg
2002
2000
1998
1996
1994
1992
1990
1988
A2 Winter Avg
1986
1984
1982
1980
1978
1976
1974
1972
B1 Winter Avg
1970
1968
1966
1964
1962
1960
1958
1956
1954
1952
1950
0.00
Fig. 2 Historical winter month (Dec 1-Feb 28) average temperatures produced by using GFDL monthly
projections (B1 and A2) and actual daily temperatures for the period of 1950-2009. Up to 2000, historical
projections under B1 and A2 are the same (the red line also represents the blue line)
Table 1 Summary statistics on GFDL historical temperature projections for summer and winter and
actual temperatures (oC) for 1950-2009
GFDL Historical projections
B1
A2
Winter avg temperature
Mean temperature
Standard deviation
Minimum temperature
Maximum temperature
Sumner avg. temperature
Mean temperature
Standard deviation
Minimum temperature
Maximum temperature
Actual
8.455
0.702
6.652
9.617
8.451
0.670
6.652
9.555
8.241
0.772
6.667
9.887
23.385
0.839
21.130
24.947
23.362
0.801
21.130
24.855
23.062
0.781
21.498
25.090
Future climate projections
Based on our daily projections for 2010-2050, we computed climate indices, GDDsummer, GDDwinter,
and chill hours, following the procedures outline in the paper. Table 2 presents the summary statistics for
the projected climate indices that are used in our acreage projections. The climate indices include
GDDsummer, GDDwinter, chill hours, precipitation, ten-year moving averages of GDDsummer,
GDDwinter, and chill hours under both B1 and A2 scenarios.
Table 2 Summary statistics of climate index (GDDsummer, GDDwinter, and chill hours) and
precipitation projections and associated ten year moving averages under B1 and A2 scenarios using
GFDL downscaled climate projections (2010-2050)
Mean
Standard
deviation
Minimum
Maximum
GDDsummer B1
3518
149
3232
3812
GDDsummer A2
3560
221
3154
4065
GDDwinter B1
1875
217
1495
2314
GDDwinter A2
1825
214
1328
2339
Chill hours B1
673
143
400
970
Chill hours A2
708
138
395
1044
Precipitation B1
1726
851
514
3886
Precipitation A2
1587
638
635
3202
Moving Avg GDDsummer B1
3524
50
3420
3620
Moving Avg GDDsummer A2
3567
59
3468
3667
Moving Avg GDDwinter B1
1842
124
1700
2048
Moving Avg GDDwinter A2
1796
50
1707
1894
Moving Avg Chill hours B1
690
62
583
801
Moving Avg Chill hours A2
740
39
663
815
The temperature patterns for the A2 and B1 scenarios are remarkably similar for the period from 2010–
2050, except for an unexpected decrease in the A2 scenario after 2035, with a concomitant increase in B1.
This is mainly due to low winter temperatures, as is evident from lower GDDwinter (Figure 4) and higher
winter chill hours (Figure 5) in A2 versus B1 in this time period. Note that GDD summer (Figure 3) and
precipitation (Figure 6) show very similar patterns for the scenarios. The greater winter warming in B1
derives directly from the climate data in the GFDL‐BCCA output runs. It appears to be an artifact of the
climate downscaling or and clearly does not reflect the long‐term pattern of greater warming in A2 by the
end of the century. Statewide projections from several other GCMs (Cayan et al. 2009) show similar
trajectories for A2 and B1 until midcentury reflecting the expectation that our current actions to mitigate
GHG emissions may have little effect in the near future.
Degree days
4500
Growing dgree days for summer months: 2010-2050
4000
3500
3000
2500
2000
2010
2015
2020
2025
2030
GDDsummer under B1
2035
2040
GDDsummer under A2
2045
2050
Fig. 3 Annual accumulated growing degree days for summer months, April through August, for 2010–
2050 under B1 and A2 scenarios using GFDL daily climate data
Degree days
Growing dgree days for winter months: 2010-2050
2500
2000
1500
1000
2010
2015
2020
2025
2030
GDDwinter under B1
2035
2040
2045
2050
GDDwinter under A2
Fig. 4 Annual accumulated growing degree days for winter months, November through May for 2010–
2050 under B1 and A2 scenarios using GFDL daily climate data
Winter chill hours: 2010-2050
Chill hours
1000
800
600
400
200
2010
2015
2020
2025
Chill hours under B1
2030
2035
2040
Chill hours under A2
2045
2050
F
Fig. 5 Annual accumulated chill hours (for November through February) for 2010–2050 under B1 and A2
scenarios using GFDL daily climate data
Precipitation: 2010-2050
Precipitation
(unit=mm)
1000
800
600
400
200
0
2010
2015
2020
2025
2030
Precipitation under B1
2035
2040
2045
2050
Precipitation under A2
Fig. 6 Annual precipitation (hundredth inches) for the period from November through April for 2010–
2050 under B1 and A2 scenarios using GFDL daily climate data
Ten year moving averages of climate index projections
The 10‐year moving averages portray broad trends more clearly and represent climate in a way consistent
with grower perceptions on climate change (Figures 7-9). These amplify the effect of the A2 winter
cooling trend by extending its effect over several years. The 10‐year moving average of GDDsummer is
more similar between the scenarios than GDDwinter or winter chill hours.
Degree days
Ten year moving average of GDDsummer: 2010-2050
3800
3600
3400
3200
3000
2010
2015
2020
2025
2030
Moving avg of GDDsummer under B1
2035
2040
2045
2050
Moving Avg of GDDsummer under A2
Fig . 7 Ten-year moving average of growing degree days (GDD) in summer months (April 1- August 31)
for 2010–2050 under B1 and A2 scenarios using GFDL daily climate data
Degree days
Ten year moving average of GDDwinter: 2010-2050
2200
2000
1800
1600
2010
2015
2020
2025
2030
Moving avg of GDDwinter under B1
2035
2040
2045
2050
Moving Avg of GDDwinter under A2
Fig. 8 Ten-year moving average of growing degree days (GDD) in winter months (November 1- May 31)
for 2010–2050 under B1 and A2 scenarios using GFDL daily climate data
Degree days
1000
Ten year moving average of winter chill hours: 2010-2050
900
800
700
600
500
2010
2015
2020
2025
Moving avg of chill hours under B1
2030
2035
2040
2045
2050
Moving avg of chill hours under A2
Fig. 9 Ten-year moving average of chill hours for 2010–2050 under B1 and A2 scenarios using GFDL
daily climate data