Climate Presentation Hyden

Climate, Weather & Farm Decisions

February, 2012
Tim Scanlon

Key Messages
• Climate and weather are different
• Difference between rain and showers
• Listen for probabilities
• Climate change/Dry spell/150yr cycle/etc
–Doesn’t matter
–Seasonal variability in WA still a big concern
–Maximising efficiency

Climate vs. Weather

Source: The Armstrong and Miller show, BBC TV

When positive
indicates the
subtropical ridge
location to the south,
thus the more positive
the lower the frontal
system on WA.

Graphic courtesy of www.bom.gov.au

Has the climate of WA changed?
Short Answer = YES

Rainfall has decreased
• Mainly early winter rainfall (May-July).
• Sudden decrease in the mid-1970s by about 15-20%.
• It was not a gradual decline but more of a switching into an
alternative rainfall regime.
• Change in the large-scale global atmospheric circulation.
• Less frequent and less intense frontal systems.
• Observed changes fit with the climate models.
• Changes in rainfall are a combination of climate change
and seasonal variability.
Temperatures have increased gradually over the last 50 years
• Day and night time (i.e. Maxima and Minima).
• Particularly in winter and autumn.
• Mostly due to climate change.
Source: Indian Ocean Climate Initiative 2005-2006 (Bates, 2008)

Graphic courtesy of www.skepticalscience.com

Causes of climate change
Greenhouse gases
• Carbon Dioxide (CO2), Methane (NH4), Nitrous oxide (NO),
Water*(H2O)
• The sun
Positive feedback
• Increased H2O (7% per 1oC)
• Reduced ice cover
• Oceans cease to be a carbon sink
• Permafrost melt (NH4)
• The main greenhouse gases comprise less than 0.5% of the atmosphere.
• Without them average global temperature ~ -20oC (not ~14oC).
• N and O >99% of the atmosphere.
• Water (H2O), CO2, CH4, NO are ~0.44% of the atmosphere.

Isohyets moving
south-west
I.e. Move your farm
50km north-east

Hyden
3 big summers Significant change
20% more likely

Source: www.bom.gov.au

Kulin
2 big summers Significant change
14.5% more likely


Seasonal Rainfall

Drop in Annual and Growing Season rainfall
– Annual 341 to 325 (85mm variation)
– GSR 246 to 216 = 30mm (June loss, 60mm variation)
2001-2011 GSR: 3 drought; 3 dry, 2 average, 1 above average,
1 wet year.
GSR = growing season rainfall

Positives?
• We know this is happening
–Decision making “easier”
• Soil moisture becomes the key indicator
• Last season gave us a lot of information
–Look at what has worked
–Water use efficiency
–What limitations?

Hyden Temperatures
Significant change


Positives?
• Wheat grows better with more CO2
–Offsets other problems like pollution
–Only to a certain point……
–WUE increases
– Causes greater stress at key periods
– Only offsets decreases in yield due to temperature changes (Wang,
1992)
• Food becomes even more important!
–Wheat is 21% of the world food (Ortiz 2008)

James Hansen et al The Open Atmospheric Science Journal, 2008, 2, 217-231

EFFECTS UPON AGRICULTURE

• Less rainfall
• Especially winter rainfall
• Higher evaporation rates
• Fewer effective rainfall events
• Reduced soil moisture and plant available water
• Less runoff due to surface water impacts
• Effects on plants’ temperature-determined
phenological events (e.g. flowering)

Factors to consider when seeding
• The amount of rain at the break (soil moisture)
• Stored soil moisture (from summer and early autumn
rain).
• The target seeding date (trade-off between getting
seeding done and hitting best range – may lose yield
with later sowing)
• Prospect of more rain in the near future
• Seasonal outlook (e.g. are there any ENSO strong signals
worth considering?).

The Future
Results from IOCI research for south-west WA projects
that relative to 1960-1990 (Bates, 2008):
By 2030
• Rainfall will decrease by between 2 to 20 percent;
• Temperatures will increase
• Summer between 0.5 to 2.1 degrees C;
• Winter between 0.5 to 2.0 degrees C;
By 2070
• Winter between 1.0 to 5.5 degrees C.

Source: David Mitchell's Soapbox, Channelflip.com

Links for more information

http://www.skepticalscience.com
http://www.bom.gov.au/climate/data/
http://www.bom.gov.au/climate/change/
http://www.agric.wa.gov.au/PC_94076.html
http://www.climatekelpie.com.au/
http://www.ioci.org.au/index.php?menu_id=22
http://www.ipcc.ch/publications_and_data/publications_ipcc_fourth_assessment_report_wg1_report_the_physical

Actual Changes
(past 109 years)


Actual changes
Last 50 years = 0.7oC increase.
Another 0.6oC increase is in the pipeline.
– I.e. 1.3oC or 2.6oC per 100 years.
– Climate forcings suggest 5oC increase will occur this
century.
Last natural change was 5oC in 10,000 years.
– I.e. 0.05oC per 100 years.

Is it us? Yes, it is.

Figure: Contributions of solar activity (dark blue), volcanic activity (red), ENSO (green), and anthropogenic
effects (purple) to global surface warming (HadCRUT observations shown in light blue), according to Lean
and Rind (2008). Graphic courtesy of www.skepticalscience.com

Figure: Bell curve showing how an increase in average temperatures leads to an increase in hot and extreme
weather. Note also that this doesn't mean there'll be no more cold weather: these cold events will become rarer
but will not disappear. Source: US Climate Change Science Program / Southwest Climate Change Network

Increase Radiative
Preindustrial Current since forcing
Gas level level 1750 (W/m2)

Carbon dioxide 280 ppm 388 ppm 108 ppm 1.46

Methane 700 ppb 1745 ppb 1045 ppb 0.48

Nitrous oxide 270 ppb 314 ppb 44 ppb 0.15

CFC-12 0 533 ppt 533 ppt 0.17

Total Forcing (CO2Equiv) 450ppm

NB: 450 ppm of CO2 equivalents is Gas Formula Contribution (%)
regarded as the upper “safe” level of H2O
Water Vapor 36 – 72 %
greenhouse gases before tipping
points occur. (Hansen, 2008) CO2
Carbon Dioxide 9 – 26 %

Methane CH4 4 – 9 %

Ozone O3 3 – 7 %

Atmospheric lifetime and GWP relative to CO2 at different time horizon for various
greenhouse gases.
Chemical Lifetime Global warming potential (GWP) for given time horizon
Gas name
formula (years) 20-yr 100-yr 500-yr
Carbon dioxide CO2 7-10 1 1 1
Methane CH4 12 72 25 7.6
Nitrous oxide N 2O 114 289 298 153
CFC-12 CCl2F2 100 11 000 10 900 5 200
HCFC-22 CHClF2 12 5 160 1 810 549
Tetrafluoromethane CF4 50 000 5 210 7 390 11 200
Hexafluoroethane C2F6 10 000 8 630 12 200 18 200
Sulphur hexafluoride SF6 3 200 16 300 22 800 32 600
Nitrogen trifluoride NF3 740 12 300 17 200 20 700

Source: http://unfccc.int/ghg_data/items/3825.php

CO2 is rising beyond
historical levels

Similar to Keeling Curve - 1965

Radiative Forcing (from IPCC 4th Report)

Temperature change relative to 1900
1940 1970 1994
Greenhouse gases 0.1 0.38 0.69
Sulfate emissions -0.04 -0.19 -0.27
Solar forcing 0.18 0.1 0.21
Volcanic forcing 0.11 -0.04 -0.14
Ozone -0.06 0.05 0.08
Net 0.19 0.17 0.53
Observed 0.26 0.21 0.52

Chance of Temperature Increases
No Policy Action Policy Action

The possible global temperature changes are indicated on each wheel, with the probabilities of each
occurring denoted by the proportion of each wheel. http://globalchange.mit.edu/resources/gamble/

Crops vs. Temperature
Rice:
• Average required 21oC to 370C, higher at tillering.
• Flowering 26.5oC to 29.50C.
• Ripening/fill between 20oC to 250C.
• 35oC for 1 hour at flowering causes sterility.
• Yield decline expected (Peng, 2004)
Wheat:
• Minimum of 3.5-5.50C.
• Optimum 20-250C.
• Maximum temperature is 350C.
• Yield decline expected (Wang, 1992)
Source: http://agropedia.iitk.ac.in/

Source: http://www.agric.wa.gov.au/objtwr/imported_assets/content/lwe/cli/foster_farre_wheat_yield_drying%20climate.pdf

This figure shows the relative fraction of
man-made greenhouse gases coming
from each of eight categories of sources,
as estimated by the
Emission Database for Global Atmospheric Research
version 3.2, fast track 2000 project.
These values are intended to provide a
snapshot of global annual greenhouse
gas emissions in the year 2000. The top
panel shows the sum over all man-made
greenhouse gases, weighted by their
global warming potential over the next 100
years. This consists of 72%
carbon dioxide, 18% methane, 8%
nitrous oxide and 1% other gases. Lower
panels show the comparable information
for each of these three primary
greenhouse gases, with the same
colouring of sectors as used in the top
chart. Segments with less than 1%
fraction are not labelled. http://
themasites.pbl.nl/en/themasites/edgar/index.html

Kaufman et al., Science, 2009, Vol 325, pp 1236-1239

But climate is cooling…

Time series of global mean heat storage (0–2000 m), measured in 108 Joules per square metre. Schuckmann 2009

But it was warmer in….

Hansen and Lebedeff (J. Geophys. Res., 92,13,345, 1987)

But it’s the sun…

Figure 1: Global temperature (red, NASA GISS) and Total solar irradiance (blue, 1880 to 1978 from
Solanki, 1979 to 2009 from PMOD). Graphic www.skepticalscience.com
http://debunking.pbworks.com/w/page/17102974/Sunspots-and-Solar-Myth

But the sun will be colder….

Rise of global temperature (relative to 1961-1990) until the year 2100 for two different emission scenarios (A1B, red, and
A2, magenta). The dashed lines show the slightly reduced warming in case a Maunder-like solar minimum should occur
during the 21st century. Source: Feulner, G., and S. Rahmstorf (2010), On the effect of a new grand minimum of solar
activity on the future climate on Earth, Geophys. Res. Lett., 37, L05707 Graphic www.skepticalscience.com

But scientists don’t agree…

Figure 1: Response to the survey question "Do you think human activity is a significant contributing
factor in changing mean global temperatures?" (Doran 2009) General public data come from a
2008 Gallup poll.

But scientists don’t agree…cont

Distribution of the number of researchers convinced by the evidence of anthropogenic climate change and unconvinced by the
evidence with a given number of total climate publications http://www.pnas.org/content/early/2010/06/04/1003187107.abstract
Graphic www.skepticalscience.com

But it used to be cooling…


But it’s the Pacific Decadal Oscillation…


But they are models….

Comparison of climate results with observations. (a) represents simulations done with only natural forcings: solar variation and
volcanic activity. (b) represents simulations done with anthropogenic forcings: greenhouse gases and sulphate aerosols. (c)
was done with both natural and anthropogenic forcings Chapter 12 IPCC 3rd report 2001

But the Antarctic is gaining ice…
Myth brought about by
confusion between sea ice
increases and land ice
losses in Antarctica.

Ice mass changes for the Antarctic ice sheet
from April 2002 to February 2009. Unfiltered
data are blue crosses. Data filtered for the
seasonal dependence are red crosses. The
best-fitting quadratic trend is shown as the green
line (Velicogna 2009). Graphic courtesy of
www.skepticalscience.com

Source: http://www.noaanews.noaa.gov/stories2010/20100728_stateoftheclimate.html

• La Nina = warmer seas near Australia
• El Nino = cooler seas near Australia
• WA less favourably impacted by La Nina
– Get more from change over years

Impact of Carbon Tax
Table 5.18: Growth in output from 2010 to 2050

Source: Treasury modelling (2011), reproduced from the Federal Government document
Securing a clean energy future
http://www.treasury.gov.au/carbonpricemodelling/content/report.asp

Impact of Carbon Tax
Table 5.6: Gross output, by industry, 2020 Table 5.7: Gross output, by industry, 2050

Climate, Weather & Farm Decisions

February, 2012
Tim Scanlon

Start with facilitated Q&A: What questions do people have about climate, weather,
climate change?
Key 3 questions from groups of 3-4 people.
Discuss and answer questions – depending upon group either just cover the questions
and start a group discussion or use as a lead in for presentation.

2

Key Messages
–Doesn’t matter

4

Key Messages
–Doesn’t matter

When positive
indicates the
subtropical ridge
location to the south,
thus the more positive
the lower the frontal
system on WA.


http://www.climatekelpie.com.au/understand-climate/weather-and-climate-
drivers/western-australia
Module 4 handouts contain weather drivers overviews.
Key point is that climate brings weather but that climate is a very complex and
interactive mechanism.

6

Has the climate of WA changed?
Short Answer = YES

Rainfall has decreased
• Mainly early winter rainfall (May-July).
• Sudden decrease in the mid-1970s by about 15-20%.
• It was not a gradual decline but more of a switching into an
alternative rainfall regime.
• Change in the large-scale global atmospheric circulation.
• Less frequent and less intense frontal systems.
• Observed changes fit with the climate models.
• Changes in rainfall are a combination of climate change
and seasonal variability.
Temperatures have increased gradually over the last 50 years
• Day and night time (i.e. Maxima and Minima).
• Particularly in winter and autumn.
• Mostly due to climate change.
Source: Indian Ocean Climate Initiative 2005-2006 (Bates, 2008)

Available at http://167.30.10.65/pdf/IOCIReport.pdf
Bates, 2008: http://www.springerlink.com/content/926058287l42120h/

8

Causes of climate change
Greenhouse gases
• Carbon Dioxide (CO2), Methane (NH4), Nitrous oxide (NO),
Water*(H2O)
• The sun
Positive feedback
• Increased H2O (7% per 1oC)
• Reduced ice cover
• Oceans cease to be a carbon sink
• Permafrost melt (NH4)
• The main greenhouse gases comprise less than 0.5% of the atmosphere.
• Without them average global temperature ~ -20oC (not ~14oC).
• N and O >99% of the atmosphere.
• Water (H2O), CO2, CH4, NO are ~0.44% of the atmosphere.

14

Positives?
• We know this is happening
–Decision making “easier”
• Soil moisture becomes the key indicator
• Last season gave us a lot of information
–Look at what has worked
–Water use efficiency
–What limitations?

15

Except for a leveling off between the 1940s and 1970s, Earth's surface temperatures
have increased since 1880. The last decade has brought the temperatures to the
highest levels ever recorded. The graph shows global annual surface temperatures
relative to 1951-1980 mean temperatures. As shown by the red line, long-term trends
are more apparent when temperatures are averaged over a five year period. (Image
credit: NASA/GISS) http://www.giss.nasa.gov/research/news/20100121/

18

Positives?
• Wheat grows better with more CO2
–Offsets other problems like pollution
–Only to a certain point……
–WUE increases
– Causes greater stress at key periods
– Only offsets decreases in yield due to temperature changes (Wang,
1992)
• Food becomes even more important!
–Wheat is 21% of the world food (Ortiz 2008)

Wang, 1992: Climate Research Volume 2 pages 131-149 http://www.int-
res.com/articles/cr/2/c002p131.pdf
Ortiz, 2008: Agriculture, Ecosystems & Environment Volume 126, Issues 1-2, June
2008, Pages 46-58
http://www.sciencedirect.com/science/article/pii/S0167880908000194

James Hansen et al The Open Atmospheric Science Journal, 2008, 2, 217-231

Over the last 400,000 years

20

21

EFFECTS UPON AGRICULTURE

• Less rainfall
• Especially winter rainfall
• Higher evaporation rates
• Fewer effective rainfall events
• Reduced soil moisture and plant available water
• Less runoff due to surface water impacts
• Effects on plants’ temperature-determined
phenological events (e.g. flowering)

22

Factors to consider when seeding
• The amount of rain at the break (soil moisture)
• Stored soil moisture (from summer and early autumn
rain).
• The target seeding date (trade-off between getting
seeding done and hitting best range – may lose yield
with later sowing)
• Prospect of more rain in the near future
• Seasonal outlook (e.g. are there any ENSO strong signals
worth considering?).

23

The Future
Results from IOCI research for south-west WA projects
that relative to 1960-1990 (Bates, 2008):
By 2030
• Winter between 0.5 to 2.0 degrees C;
By 2070
• Winter between 1.0 to 5.5 degrees C.

Bates, B. C., Hope, P., Ryan, B., Smith, I.
Charles, S. 2008 Key findings from the Indian
Ocean Climate Initiative and their impact on
policy development in Australia Climate Change
(2008) 89:339-354
http://www.springerlink.com/content/926058287l42120h/

24

So What Have We Learnt?

Links for more information

http://www.skepticalscience.com
http://www.bom.gov.au/climate/data/
http://www.bom.gov.au/climate/change/
http://www.agric.wa.gov.au/PC_94076.html
http://www.climatekelpie.com.au/
http://www.ipcc.ch/publications_and_data/publications_ipcc_fourth_assessment_report_wg1_report_the_physical_science_basis.htm

Ask for sceptics and reasons why.
Alternatively, if already covered in questions at the start, use as a links page.

Figure: Bell curve showing how an increase in average temperatures leads to an increase in hot and extreme
weather. Note also that this doesn't mean there'll be no more cold weather: these cold events will become rarer
but will not disappear. Source: US Climate Change Science Program / Southwest Climate Change Network

Figure 1: Bell curve showing how an increase in average temperatures leads to an
increase in hot and extreme weather. Note also that this doesn't mean there'll be no more
cold weather: these cold events will become rarer but will not disappear. Source:
US Climate Change Science Program / Southwest Climate Change Network

30

Increase Radiative
Preindustrial Current since forcing
Gas level level 1750 (W/m2)

Carbon dioxide 280 ppm 388 ppm 108 ppm 1.46

Methane 700 ppb 1745 ppb 1045 ppb 0.48

Nitrous oxide 270 ppb 314 ppb 44 ppb 0.15

CFC-12 0 533 ppt 533 ppt 0.17

Total Forcing (CO2Equiv) 450ppm

NB: 450 ppm of CO2 equivalents is Gas Formula Contribution (%)
regarded as the upper “safe” level of H2O
Water Vapor 36 – 72 %
greenhouse gases before tipping
points occur. (Hansen, 2008) CO2
Carbon Dioxide 9 – 26 %

Methane CH4 4 – 9 %

Ozone O3 3 – 7 %

Hansen J, Sato M, et al. (2008) Target atmospheric CO2: Where should humanity aim?
The Open Atmospheric Science Journal 2, 217-231. http://arxiv.org/abs/0804.1126

Atmospheric lifetime and GWP relative to CO2 at different time horizon for various
greenhouse gases.
Chemical Lifetime Global warming potential (GWP) for given time horizon
Gas name
formula (years) 20-yr 100-yr 500-yr
Carbon dioxide CO2 7-10 1 1 1
Methane CH4 12 72 25 7.6
Nitrous oxide N2 O 114 289 298 153
CFC-12 CCl2F2 100 11 000 10 900 5 200
HCFC-22 CHClF 2 12 5 160 1 810 549
Tetrafluoromethane CF4 50 000 5 210 7 390 11 200
Hexafluoroethane C2F6 10 000 8 630 12 200 18 200
Sulphur hexafluoride SF6 3 200 16 300 22 800 32 600
Nitrogen trifluoride NF3 740 12 300 17 200 20 700

Source: http://unfccc.int/ghg_data/items/3825.php

CO2 is rising beyond
historical levels

Similar to Keeling Curve - 1965

Keeling Curve
Graphic from Wikipedia, the free encyclopaedia
The Keeling Curve: Atmospheric CO2 concentrations as measured at Mauna Loa Observatory
The Keeling Curve is a graph showing the variation in concentration of atmospheric carbon dioxide since 1958. It is based on
continuous measurements taken at the Mauna Loa Observatory in Hawaii under the supervision of Charles David Keeling.
Keeling's measurements showed the first significant evidence of rapidly increasing carbon dioxide levels in the atmosphere.
Many scientists credit Keeling's graph with first bringing the world's attention to the effects that human activity was having on
the Earth's atmosphere and climate.[1]
Charles David Keeling, of the Scripps Institution of Oceanography at UC San Diego, was the first person to make frequent regular
measurements of the atmospheric carbon dioxide (CO2) concentration, taking readings at the South Pole and in Hawaii from
1958 onwards.[2]
Prior to Keeling, the concentration of carbon dioxide in the atmosphere was thought to be affected by constant variability. Keeling
had perfected the measurement techniques and observed "strong diurnal behaviour with steady values of about 310 ppm in
the afternoon" at three locations: (Big Sur near Monterey, the rain forests of Olympic Peninsula and high mountain forests in
Arizona).[3] By measuring the ratio of two isotopes of carbon, Keeling attributed the diurnal change to respiration from local
plants and soils, with afternoon values representative of the "free atmosphere". By 1960, Keeling and his group established
the measurement record that was long enough to see not just the diurnal and seasonal variations, but also a year-on-year
increase that roughly matched the amount of fossil fuels burned per year. In the article that made him famous, Keeling
observed, "at the South Pole the observed rate of increase is nearly that to be expected from the combustion of fossil fuel".[4]
Mauna Loa measurements
Due to funding cuts in the mid-1960s, Keeling was forced to abandon continuous monitoring efforts at the South Pole, but he
scraped together enough money to maintain operations at Mauna Loa, which have continued to the present day.[5]
The measurements collected at Mauna Loa show a steady increase in mean atmospheric CO2 concentration from about 315 parts
per million by volume (ppmv) in 1958 to 385 ppmv as of June 2008.[6][7] This increase in atmospheric CO2 is considered to be
largely due to the combustion of fossil fuels, and has been accelerating in recent years. Since carbon dioxide is a
greenhouse gas, this has significant implications for global warming. Measurements of carbon dioxide concentration in ancient
air bubbles trapped in polar ice cores show that mean atmospheric CO2 concentration has historically been between 275 and
285 ppmv during the Holocene epoch (9,000 BCE onwards), but started rising sharply at the beginning of the nineteenth
century.[8] However, analyses of stomatal frequency in tree leaves indicate that mean atmospheric CO2 concentration may
have reached 320 ppmv during the Medieval Warm Period (800–1300 CE) and 350 ppmv during the early Holocene.[9][10]
Though Mauna Loa is not an active volcano, Keeling and collaborators made measurements on the incoming ocean breeze and
above the thermal inversion layer to minimize local contamination from volcanic vents. In addition, the data are normalized to
negate any influence from local contamination.[11] Measurements at many other isolated sites have confirmed the long-term
trend shown by the Keeling Curve,[12] though no sites have a record as long as Mauna Loa.[13]
The Keeling Curve also shows a cyclic variation of about 5 ppmv in each year corresponding to the seasonal change in uptake of CO2
by the world's land vegetation. Most of this vegetation is in the Northern hemisphere, since this is where most of the land is
located. The level decreases from northern spring onwards as new plant growth takes carbon dioxide out of the atmosphere
through photosynthesis and rises again in the northern fall as plants and leaves die off and decay to release the gas back into
the atmosphere.[14]
Due in part to the significance of Keeling's findings,[5] the NOAA began monitoring CO2 levels worldwide in the 1970s. Today, CO2
levels are monitored at about 100 sites around the globe.[1]
Carbon dioxide measurements at the Mauna Loa observatory in Hawaii are made with a type of infrared spectrophotometer(
capnograph invented in 1864 by John Tyndall) called a nondispersive infrared sensor[15]
Keeling died in 2005. Supervision of the measuring project was taken over by his son, , a climate science professor at the Scripps

Temperature change relative to 1900
1940 1970 1994
Greenhouse gases 0.1 0.38 0.69
Sulfate emissions -0.04 -0.19 -0.27
Solar forcing 0.18 0.1 0.21
Volcanic forcing 0.11 -0.04 -0.14
Ozone -0.06 0.05 0.08
Net 0.19 0.17 0.53
Observed 0.26 0.21 0.52

This figure, based on Meehl et al. (2004), shows the ability with which a
global climate model (the DOE PCM [1]) is able to reconstruct the
historical temperature record and the degree to which the associated temperature
changes can be decomposed into various forcing factors. The top part of the figure
compares a five year average of global temperature measurements (Jones and Moberg
2001) to the Meehl et al. results incorporating the effects of five predetermined forcing
factors: greenhouse gases, man-made sulfate emissions, solar variability, ozone changes
(both stratospheric and tropospheric), and volcanic emissions (including natural
sulfates). The time history and radiative forcing effectiveness for each of these factors
was specified in advance and was not adjusted to specifically match the temperature
record.
Also shown are grey bands indicating the 68% and 95% range for natural variability in
the five year average of temperature as determined from multiple simulations with
different initial conditions. In other words, the bands indicate the estimated size of
fluctuations that are expected to result from changes in weather rather than changes in
climate. Ideally the model should be able to reconstruct temperature variations to within
about the tolerance specified by these bands. Though the model captures the gross
features of twentieth century climate change, it remains likely that some of the
differences between model and observation reflect the limitations of the model and/or
our understanding of the histories of the observed forcing factors.
In the lower portion of the figure are the results of additional simulations in which the
model was operated with only one forcing factor at a time. A key conclusion of the
Meehl et al. (2004) work is that the model response to all factors combined is
approximately equal to the sum of the responses to each of the factors taken individually.
They conclude therefore that it is reasonable to discuss how the evolving man-made and
natural influences individually impact climate. Meehl et al. attribute most of the 0.52 °C 35

Crops vs. Temperature
Rice:
• Average required 21oC to 370C, higher at tillering.
• Flowering 26.5oC to 29.50C.
• Ripening/fill between 20oC to 250C.
• 35oC for 1 hour at flowering causes sterility.
• Yield decline expected (Peng, 2004)
Wheat:
• Minimum of 3.5-5.50C.
• Optimum 20-250C.
• Maximum temperature is 350C.
• Yield decline expected (Wang, 1992)
Source: http://agropedia.iitk.ac.in/

Peng, 2004: PNAS Vol 101, Issue 27, pages 9971-9975
http://www.pnas.org/content/101/27/9971.long
Wang, 1992: Climate Research Volume 2 pages 131-149 http://www.int-
res.com/articles/cr/2/c002p131.pdf
Further reading:
http://www.mssanz.org.au/modsim05/papers/howden.pdf
http://www.agric.wa.gov.au/objtwr/imported_assets/content/lwe/cli/foster_farre_wheat_
yield_drying%20climate.pdf
http://www.garnautreview.org.au/CA25734E0016A131/WebObj/01-BWheat/$File/01-B
%20Wheat.pdf
Ortiz, 2008: Agriculture, Ecosystems & Environment Volume 126, Issues 1-2, June
2008, Pages 46-58
http://www.sciencedirect.com/science/article/pii/S0167880908000194

38

Source: http://www.agric.wa.gov.au/objtwr/imported_assets/content/lwe/cli/foster_farre_wheat_yield_drying%20climate.pdf

Further reading: http://www.garnautreview.org.au/CA25734E0016A131/WebObj/01-
BWheat/$File/01-B%20Wheat.pdf

39

Except for a leveling off between the 1940s and 1970s, Earth's surface temperatures
have increased since 1880. The last decade has brought the temperatures to the highest
levels ever recorded. The graph shows global annual surface temperatures relative to
1951-1980 mean temperatures. As shown by the red line, long-term trends are more
apparent when temperatures are averaged over a five year period. (Image credit:
NASA/GISS) http://www.giss.nasa.gov/research/news/20100121/

41

As seen by the blue point farthest to the right on this graph, 2009 was the warmest year
on record in the Southern Hemisphere. (Image credit: NASA/GISS)
http://www.giss.nasa.gov/research/news/20100121/

42

Kaufman et al., Science, 2009, Vol 325, pp 1236-1239

Science 4 September 2009:
Vol. 325 no. 5945 pp. 1236-1239
Recent Warming Reverses Long-Term Arctic Cooling
Darrell S. Kaufman1,,
David P. Schneider2,
Nicholas P. McKay3,
Caspar M. Ammann2,
Raymond S. Bradley4,
Keith R. Briffa5,
Gifford H. Miller6,
Bette L. Otto-Bliesner2,
Jonathan T. Overpeck3,
Bo M. Vinther7 and
Arctic Lakes 2k Project Members†
+ Author Affiliations
1School of Earth Sciences and Environmental Sustainability, Northern Arizona University, Flagstaff, AZ 86011, USA.
2Climate and Global Dynamics Division, National Center for Atmospheric Research, Boulder, CO 80305, USA.
3Department of Geosciences, University of Arizona, Tucson, AZ 85721, USA.
4Department of Geosciences, University of Massachusetts, Amherst, MA 01003, USA.
5Climatic Research Unit, University of East Anglia, Norwich NR4 7TJ, UK.
6Institute of Arctic and Alpine Research, University of Colorado, Boulder, CO 80309, USA.
7Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark.
*To whom correspondence should be addressed. E-mail: darrell.kaufman@nau.edu
Abstract
The temperature history of the first millennium C.E. is sparsely documented, especially in the Arctic. We present a synthesis of
decadally resolved proxy temperature records from poleward of 60°N covering the past 2000 years, which indicates that a pervasive
cooling in progress 2000 years ago continued through the Middle Ages and into the Little Ice Age. A 2000-year transient climate
simulation with the Community Climate System Model shows the same temperature sensitivity to changes in insolation as does our
proxy reconstruction, supporting the inference that this long-term trend was caused by the steady orbitally driven reduction in
summer insolation. The cooling trend was reversed during the 20th century, with four of the five warmest decades of our 2000-year-
long reconstruction occurring between 1950 and 2000.

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But it was warmer in….

Hansen and Lebedeff (J. Geophys. Res., 92,13,345, 1987)

Fig. 2. Global surface temperature computed for scenarios A, B, and C (12), compared with
two analyses of observational data. The 0.5°C and 1°C temperature levels, relative to
1951–1980, were estimated (12) to be maximum global temperatures in the Holocene
and the prior interglacial period, respectively. Hansen and Lebedeff [J. Geophys. Res.,
92,13,345, 1987]
Annual mean global surface air temperature computed for scenarios A, B and C.
Observational data are an update of the analysis of Hansen and Lebedeff [J. Geophys. Res.,
92,13,345, 1987]. Shaded area is an estimate of the global temperature during the peak of
the current interglacial period (the Altithermal, peaking about 6,000 to 10,000 years ago,
when we estimate that global temperature was in the lower part of the shaded area) and the
prior interglacial period (the Eemian period, about 120,000 years ago, when we estimate
that global temperature probably peaked near the upper part of the shaded area). The
temperature zero point is the 1951-1980 mean.

Medieval warm period is largely mythical. Yes it was warm during that period, but
Greenland has had an icesheet for 400,000 to 800,000 years (at least), and statements
that it was warmer then than now is false. This is based upon early incomplete science
data sets, thus since collecting more data the historical temperatures have been better
understood. Also interesting to note that the skeptics use the first IPCC graphs for this, but
won’t use the more complete graphs.

Altithermal = A dry postglacial interval centered about 5500 years ago during which
temperatures were warmer.
Eemian = The Eemian was an interglacial period which began about 130,000 years ago and
ended about 114,000 years ago. It was the second-to-latest interglacial period of the

But it’s the sun…

Figure 1: Global temperature (red, NASA GISS) and Total solar irradiance (blue, 1880 to 1978 from
Solanki, 1979 to 2009 from PMOD). Graphic www.skepticalscience.com

http://www.skepticalscience.com/solar-activity-sunspots-global-warming-advanced.htm

Sceptic comments
It's the sun: "Over the past few hundred years, there has been a steady increase in the numbers of sunspots, at the
time when the Earth has been getting warmer. The data suggests solar activity is influencing the global climate causing
the world to get warmer."
What the science says...
In the last 35 years of global warming, sun and climate have been going in opposite directions
Until about 1960, measurements by scientists showed that the brightness and warmth of the sun, as seen from the
Earth, was increasing. Over the same period temperature measurements of the air and sea showed that the Earth was
gradually warming. It was not surprising therefore for most scientists to put two and two together and assume that it was
the warming sun that was increasing the temperature of our planet.
However, between the 1960s and the present day the same solar measurements have shown that the energy from the
sun is now decreasing. At the same time temperature measurements of the air and sea have shown that the Earth has
continued to become warmer and warmer. This proves that it cannot be the sun; something else must be causing the
Earth's temperature to rise.
So, while there is no credible science indicating that the sun is causing the observed increase in global temperature, it's
the known physical properties of greenhouse gasses that provide us with the only real and measurable explanation of
global warming.

Bit more:
As supplier of almost all the energy in Earth's climate, the sun has a strong influence on climate. A comparison of sun and climate
over the past 1150 years found temperatures closely match solar activity (Usoskin 2005). However, after 1975, temperatures rose
while solar activity showed little to no long-term trend. This led the study to conclude, "...during these last 30 years the solar total
irradiance, solar UV irradiance and cosmic ray flux has not shown any significant secular trend, so that at least this most recent
warming episode must have another source."
In fact, a number of independent measurements of solar activity indicate the sun has shown a slight cooling trend since 1960, over
the same period that global temperatures have been warming. Over the last 35 years of global warming, sun and climate have been
moving in opposite directions. An analysis of solar trends concluded that the sun has actually contributed a slight cooling influence
in recent decades (Lockwood 2008).

Figure 1: Annual global temperature change (thin light red) with 11 year moving average of temperature (thick dark
red). Temperature from NASA GISS. Annual Total Solar Irradiance (thin light blue) with 11 year moving average of TSI (thick dark
blue). TSI from 1880 to 1978 from Solanki. TSI from 1979 to 2009 from PMOD.
Other studies on solar influence on climate
This conclusion is confirmed by many studies finding that while the sun contributed to warming in the early 20th Century, it has
had little contribution (most likely negative) in the last few decades:
Erlykin 2009: "We deduce that the maximum recent increase in the mean surface temperature of the Earth which can be ascribed to
solar activity is 14% of the observed global warming."
Benestad 2009: "Our analysis shows that the most likely contribution from solar forcing a global warming is 7 ± 1% for the 20th
century and is negligible for warming since 1980."
47
Lockwood 2008: "It is shown that the contribution of solar variability to the temperature trend since 1987 is small and downward;

But they are models….

Comparison of climate results with observations. (a) represents simulations done with only natural forcings: solar variation and
volcanic activity. (b) represents simulations done with anthropogenic forcings: greenhouse gases and sulphate aerosols. (c)
was done with both natural and anthropogenic forcings Chapter 12 IPCC 3rd report 2001

Also use Sir David Attenborough’s video to support this.

53

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