20th Century Climate Change Data, Causation

1
20th Century Climate Change Data, Causation
2
Current Climate Change Data and Causes

• This is how Ill group the slides in this
  presentation
• A. Global Temperatures
• B. Sea Level Changes
• C. Arctic Ocean Ice
• D. Glacier Retreats
• E. Permafrost and methane

3
A. Global Temperatures

• Temperature rise in the Industrial Age in the
  context of the past recent and geologic time
  scales

4
The Global Temperature Record for the past 150
Years Can Be Roughly Divided into 4 Regimes
5
1. Up to 1912

• Human generated GHGs are still fairly small.
  Cars are a rarity, human population is a small
  fraction of todays.
• We are still in the general regime of the past
  interglacial 6000 years, which shows little
  trend in global temperatures
• However, an unusually large number of major
  volcanic eruptions added significant cooling
  stratospheric aerosols Krakatoa 1883
  (climatically strongest in modern record, see
  especially Gleckler et.al. 2006), Santa Maria
  (1902, one of the 5 biggest of the past 200
  years), Katmai 1912 (largest of the 20th century)
• The Katmai eruption set the minimum of global
  temperatures for the 20th century (and very
  likely beyond)

6
2. Period 1912 to 1942

• The long term solar cycles show a modulation such
  that successive solar maxima are roughly similar,
  and change slowly, over roughly century time
  scales
• Sunspot numbers are a fairly good proxy for solar
  activity, and recall that there is a 0.1
  modulation in the solar luminosity with the solar
  cycle, and stronger solar cycles are associated
  with higher solar luminosity of similar scale
• During this period, solar sunspot maxima were
  trending higher, and the inferred solar
  luminosity (we have no direct measurements of
  solar luminosity back in those days) was rising
• Climate models show that in addition to rising
  anthropogenic CO2, solar activity likely
  accounted for a significant part of the
  temperature rise seen at this time, with
  deforestation and emergence from the Katmai
  eruption cooling also being significant.
• Also contributing, was a quiet period of no
  significant volcanic eruptions to inject cooling
  aerosols, compared to the 1883-1912 period.
• See next slide.

7
Climate modelling (e.g. Hansen 2005) shows
increasing solar activity and accompanying
luminosity rise likely accounts for a part of
1900-1945 global temperature rise. Forcing level
is not shown on these graphs. Timing is what is
being shown.
8
3. Period WWII to 1970

• Post WWII period of rapid rebuilding and rapid
  industrialization
• While CO2 levels are rising, what is rising
  faster is the smoky, choking pollution of
  aerosols associated with coal burning, rapidly
  rising vehicle-miles, and power plants.
• Unburned hydrocarbons combine with sunlight, and
  water with sulfates to produce hydrosulfuric acid
  droplets and other particles which reflect
  incoming sunlight and cool the surface.
• The so-called aerosol indirect effect - These
  particles are also large enough to act as cloud
  nucleation sites and increase low clouds (this
  air pollution usually hangs low to the ground due
  to temperature inversions).
• (I grew up in L.A. in this period. You youngsters
  cannot believe how bad it was back then. You were
  lucky to be able to see 2 miles through the smog,
  and seeing the San Gabriel Mountains 20 miles
  away was a rarity.

9

• At the same time, World War II destroyed a lot of
  life and industrial capability, and it took some
  time for this to be rebuilt. There was a period
  of reduced growth in greenhouse gases at the
  beginning of this period.
• Also, the rising solar luminosity (as inferred
  from the sunspot cycle) came to a top in mid
  1950s and has been declining every since.
• The combination of lowered rate of GHG emission
  and much higher anthropogenic reflective
  pollutants, and a halt to solar-induced
  luminosity increases was enough to halt global
  warming and keep temperatures roughly constant
  during this 25 year period.

10
The Pennsylvania Smog Attack of 1948
11
London Smog 1952, killed 12,000 people
12
London THE Smog Capital of that Time
13
But L.A. Provided Strong Competition
14
Los Angeles Famous then as the of Smog Capitol
of the United States
15
New York Not Much Better
16
The Smog Machine!
17
Smog Particles from R. Healy (looks like a
couple of pollen grains at upper left as well)
18
4. 1970-Today

• Greenhouse gas emissions accelerate
• The Clean Air Act of 1970 and other air pollution
  laws in the U.S. and Europe cause a significant
  reduction in cooling aerosols, while China and
  Asia make up for these improvements with large
  post-Mao industrialization, largely coal-fired.
  Net global aerosol effect is approximately a
  wash, as can be seen in Hansen et.al. 2005.
• Solar and other effects are negligible compared
  to greenhouse gas emissions, primarily CO2 from
  oil, gas, gasoline, and coal burning
• Strong and accelerating greenhouse warming
  dominates climate forcings

19
14 sec video Worldwide Temps 1976-2012

• https//www.youtube.com/watch?featureplayer_embed
  dedvZAp1o-669xc

20

• Heating and Cooling Forcings to the Earths Heat
  Budget (from Hansen et.al. 2005). Forcings
  calibrated from observations. Combined with the
  GISS Climate Model, they reproduce observed
  global temperature in detail very well. See next
  slide

21

• (from Hansen et.al. 2005) Before 1900, the
  observed curve is based on observations at
  meteorological stations and the model is sampled
  at the same points, whereas after 1900 the
  observations include sea surface temperatures for
  the ocean area, and the model is the true global
  mean (Hansen et. al. 2001).

22
Notes on Climate Forcings from Hansen et. al. 2005

• Effective forcings are derived from five-member
  ensembles of 120-year simulations for each
  individual forcing and for all forcings acting at
  once see (9) and supporting online material.
  The sum of individual forcings differs slightly
  from all forcings acting at once because of
  nonlinearities in combined forcings and unforced
  variability in climate simulations.
• This is the ozone forcing in our principal
  IPCC simulations it decreases from 0.24 to 0.22
  W/m2 when the stratospheric ozone change of
  Randel and Wu (S1) is used
• Ozone and black carbon forcings are less than
  they would be for conventional forcing
  definitions (11), because their efficacy is
  only 75 (9)

23
IPCC AR4 (2007) Climate Forcings Human and
Natural from 1750-present
24
2. Sea Level Changes

• Thermal, melt water, salinity, geoid changes and
  relation to global temperatures

25
On the 60 year time scale, sea level rises for
two reasons, both are climate-related

• 1. Thermal expansion of warmer water (simple
  physics. Observe temperature profile of the
  ocean, integrate, derive the thermal expansion)
• 2. Melting of continental permanent ice
  (glaciers, land ice caps)
• While thermal expansion has provided most of the
  total of the past 100 years continental melt is
  rapidly increasing, and now contributing 1/3 of
  the current sea level rise rate.
• Sea Level Rise rate 1.8mm/year avgd over past
  100 years, but is 3.3mm/year avgd over the past
  20 years.
• Note that sea ice melting contributes nothing to
  sea level rise, since floating ice already
  displaces water (Archimedes Principle). Thus,
  melting of the Arctic Ocean ice happening now is
  not contributing to sea level rise
• On longer time scales, there is minor
  contributions from slow rebound of the land from
  the last Ice Age (loss of heavy glaciation causes
  continental land to float a bit higher, and this
  process is very slow).
• On time scales of a few years and shorter, there
  are many factors affecting sea level tides, El
  Ninos, tsunamis, changing atmospheric pressure
  associated with storms, floods and associated
  salinity changes
• 34 second video of Greenland areas of ice melting
  (in red)

26
(No Transcript)
27
Sea Level Rise vs. Time and Place

• El Ninos tend to cause sharper rises in sea
  level where the warm surface waters are, from the
  thermal expansion of water
• La Ninas (the cold surface water phase) does the
  opposite
• The height of the geoid (the gravitational
  potential surface of the Earth a surface
  parallel to sea level if all other factors are
  ignored) changes near Greenland and Antarctica
  especially, as glacial melt takes mass away from
  these continental masses
• Hence, the rate of sea level rise varies from
  place to place at different times. Must take
  account of geoid changes (straight-forward
  gravity) and other data sampled widely in
  location and time to get it right.
• The following data shows the many tidal gauges
  and satellite measurements are doing a good job
  of tracking global sealevel rise

28
(No Transcript)
29
(No Transcript)
30
How does this rise rate compare with Ice Age
transitions? Red line is 1.8mm/yr 20th century
average. Recent rate is higher 1993-2003
satellite observed rate is 3.3mm/yr
31
GRACE Satellite uses gravity to measure total ice
mass loss from Greenland. Ice loss is
accelerating.
32
Estimates of total Antarctic land ice changes and
approximate sea level contributions using many
different measurement techniques. Adapted from
The Copenhagen Diagnosis. (CH Chen et al. 2006,
WH Wingham et al. 2006, R Rignot et al. 2008b,
CZ Cazenave et al. 2009 and VVelicogna 2009)
(Source here)
33

• 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).

34

• Monthly changes in Antarctic ice mass, in
  gigatons, as measured by NASAs GRACE satellites
  from 2003 to 2011. Results from five different
  IMBIE team members using different methods. The
  data have been adjusted to reflect new models of
  post-glacial rebound.(Shepherd et.al. 2012).

35
What about glaciers globally? Maybe its just
Greenland and Antarctic glaciers that are melting?

• No.

36
Global Melt of Glaciers, in equivalent water
thickness (black boxes, m/yr), and cumulative
total thickness loss (red boxes, right scale,
meters). Glacier melt is clearly accelerating
rapidly
37
Annual change in global glacier melting to sea
level rise (left axis, mm of water equivalent,
mm/yr) and cumulative value (right axis, mm),
based on surface area-weighted mass balance
observations. (source)
38
The speed of melting (meters of glacier depth per
year) of 23 different Antarctic glaciers vs. the
temperature of the seawater into which they
contact, where 0 is the freezing point of (salt)
water. Clearly the rate of melting rises rapidly
with even small temperature differences above the
freezing point. Data from satellites and ground
surveys (Rignot Jones 2002)
39
Arctic Ocean Ice Cover Dropping More Rapidly
than the 2007 IPCC AR4 models
40
Arctic ice coverage is dropping in all seasons,
not just summer
41
Not just ice coverage area, but ice volume is
dropping even more dramatically, as the permanent
ice rapidly disappears, leaving only thin
seasonal ice
42
Summer Sea Ice Area past 1,450 years. In 2012, a
new record low of 3.5x106 km2. That is less
than half the value of the bottom point of this
curve. See the Latest data
43
Lets Put Recent Global Warming in Context of the
Last 1000 Years

• From Mann et.al. 1999. The Hockey Stick made
  famous in An Inconvenient Truth

44
Temperature Proxies for Century, Millenium Time
Scales

• (See Mann et.al. 2008 and here, for more
  details), but briefly
• Foraminifora growth sensitive to temperature
  different for different species. Preserved in
  sediments
• Tree rings show good correlation to other
  proxies, until the 20th century (likely because
  CO2 levels also affect tree rings and CO2 levels
  now far above typical values of past 1000 years
• Stalagmites annual growth ring thickness (water
  from above) sensitive to temperature and climate
  in general
• Ice cores trapped air bubbles preserve
  atmosphere, and isotope ratios are sensitive to
  temperature. Also trap pollen, species sensitive
  to temperature
• Pollen species composition in sediments from
  lakes, layering showing annual runoff, charcoal
  shows major fires which can be cross correlated
  with other data
• Borehole temperatures surface temperatures
  conduct downward through the ground, and deep
  measurements contain information on ancient
  temperatures. See NOAAs site on borehole science

45
Given the importance, the work was re-done with a
wider range of temperature proxy assumptions and
additional care to avoid statistical
over-fitting. Still a Hockey stick. Note the
Medieval Warm period is actually a Northern
Hemisphere phenomenon, not global.
46
Glacier length change from temperature proxies
Old photos, and written accounts. Still a hockey
stick
47
Global surface temperature change over the last
five centuries from boreholes (thick red line).
Shading represents uncertainty. Blue line is a
five year running average of HadCRUT global
surface air temperature (Huang 2000). Borehole
data confirms the other temperature proxies.
48
Jones and Mann (2004) temperature reconstructions
using proxies, now going back almost 2000 years,
with global temperatures at the bottom pane.
Actual instrumental temperatures shown in red.
Proxies and instruments both agree - still a
Hockey Stick
49
Other Climate Change Effects

• Global phytoplankton has declined by an alarming
  40 since 1950, as warmer, more stratified ocean
  surface waters inhibit nutrient mixing from below
  and thus limit growth
• The stratosphere is cooling, as rising
  stratospheric CO2 gets less IR from below but
  radiates more IR because of collisional
  excitation followed by radiative de-excitation.
  We showed this earlier in the course.

50
(No Transcript)
51
Night Temperatures Rising Faster than Day
Temperatures

• causes a decrease in the daily temperature
  range, which has been observed (Braganza 2004).
• This too is a unique prediction of Greenhouse
  Effect warming (Alexander 2006). Why? Because
  temperatures reflect the integrated heating that
  has already happened during the day, so that peak
  temperatures occur in the late afternoon, not at
  noon as you'd naively expect if there were no
  lag. The hot ground can't efficiently radiate
  away this heat because it is trapped by CO2, and
  this keeps night-time temperatures warmer.
• Daytime temperatures are warmer too, but not as
  much at night time temps because it is not
  increased incoming sunlight that is causing
  Global Warming, it is human-caused greenhouse
  gases inhibiting re-radiated cooling, which
  happens mostly late evening, AFTER the incoming
  solar heating.
• A particularly dramatic demonstration of this can
  be seen in the mid/late 20th century data, when
  cooling by human-generated aerosol pollution
  caused daytime temperatures to stay roughly
  constant in spite of increasing CO2, while
  nighttime temperature actually increased (Wild,
  Ohmura, and Makowski 2007).

52
Night-time minimum temps are rising faster than
are daytime maximum temps, although both are
rising. This is a unique signature of GHG-caused
warming
53
Why is This Happening to Us!?

• Why?... Us! We human beings - were doing it!
  Weve raised CO2 levels from 280ppm to 400ppm in
  just the last 130 years, and its accelerating
  rapidly.
• How? By sheer number and dominance. As recently
  as 1900, wild mammals made up 50 of the land
  biomass. Now, only 3. Humans and their livestock
  make up 97 of the vertebrate biomass on land
  (Bodley 2008), and 72 of ALL vertebrate biomass
  on land or sea. (90 of the large fish have
  already been fished out, so that makes our
  domination that much easier).
• 36 of the primary productivity of the entire
  planet has been diverted to humans (Haberl,
  et.al. 2012)

54
This 2008 graph is already out of date.
Population passed 7 Billion in 2012. Human
population is rising now at an amazing and
unsustainable rate of 1 billion additional people
every 13 years.
55

• Were forcing CO2 into the atmosphere at a rapid
  rate, taking the cumulative carbon sequestration
  of hundreds of millions of years (the
  Carboniferous Era) and burning it all at once
  in a geologic instant.

56
CO2 Levels from ice cores, for the past 1
million years
57
Progressively expanded time scale needed to show
how incredibly rapid is the CO2 rise of today vs.
geologic past
58
CO2 Levels - past 60 years
59
(No Transcript)
60
But maybe the CO2 is not from us, but instead
from volcanoes or something else?

• No. The CO2 is ours.
• Volcanoes put out only 1 of the CO2 that humans
  inject annually into the atmosphere
• How do we know that CO2 is ours? There are many
  independent confirmations its ours, which Ill
  number as follows.

61
1. Were injecting far more than enough CO2 into
the atmosphere to account for the observed rise
(some goes into the ocean, some into plants and
soil)
62
Global Temperatures vs Atmospheric CO2 vs CO2
Emissions by Humans Last 1000 Years.
63
2. Note how the growth rate of CO2 drops during
economic recessions. 10 year averages are the
unmarked bars. Ive added economic recessions
(Fed data) labeled with years. The oil shock
recessions of 74 (Arab oil embargo) and the 91
(Gulf War) are particularly obvious
64

65
Methane Coming from domesticated cattle, and
from melting permafrost and peat, is 25x more
powerful as a greenhouse gas than CO2, per kg
(avged over 100 yrs)

• Melting Permafrost Accelerating Global Warming
  methane trapped in melting Arctic Lakes is being
  released
• K. Anthony (U. Fairbanks) on Arctic lake methane
• Note, CH4 oxidizes to H2O CO2. The residence
  time of a CH4 molecule in the atmosphere is about
  10 years. Both H2O and CO2 are less powerful
  greenhouse gases than methane.

66
Fraction of total emission of carbon which (top
frame) remains in the atmosphere, (middle) taken
up by land biosphere, and (bottom) taken up by
ocean. Time period is 1960 2007. Note as the
ocean absorbs more CO2 and also warms, it is
becoming less effective at soaking up additional
CO2. The opposite is true on land (sorry for the
terrible repro of this tiny graph)
67
Deforestation Human Fingerprint Since Dawn of
Civilization

• Tropical deforestation, as countries scramble to
  sell off their timber and clear cut so they can
  grow cattle (and soybeans, sugar), accounts for
  nearly 20 of carbon emissions (Canadell et.al.
  2007)
• In Indonesias main island of Sumatra, home of
  the last Sumatran Rhinos, deforestation destroys
  5 football fields worth of rainforest per minute.
• Forests remove 2.4 billion tons of carbon from
  atmosphere per year (Canadell et.al. 2011)
• Regrowth from cessation of tropical forest
  clearing shows rapid carbon uptake into trees,
  and also into root systems underground
• But Slash / burn adds significant carbon to
  atmosphere, as has been done for thousands of
  years, and still goes on in the Amazon and other
  places.

68
Deforestation Produces about 1/3 as much CO2 per
year as fossil fuel burning
69
(No Transcript)
70
(No Transcript)
71
Causes of Amazon deforestation Cattle Ranches,
Mostly. Demand from rapid proliferation of fast
food outlets world wide
72
(No Transcript)
73
Deforested Land Shown in Red NASA image
74
Effects of Deforested Land on Climate

• 1. Carbon burned or otherwise put back into the
  atmosphere as CO2
• 2. Loss of photosynthesis loss of ability to
  pull CO2 out of atmosphere
• 3. Desertification of land this may actually
  cause some cooling (although I cant find data),
  via higher reflectivity of land vs. forest
• 4. Healthy forest returns ¾ of rainfall back to
  the atmosphere where it can rain out elsewhere.
  Deforested land returns only ¼ of rain water back
  to the atmosphere for further downwind
  rainmaking, instead causing severe runoff,
  erosion, loss of topsoil, and loss to the ocean

75
Key Points Current Climate Change and Global
Warming (GW)

• Solar luminosity, cosmic ray modulation, show no
  secular change since 1950s cannot be causing
  GW
• 20-21st Century climate 3 regimes and their
  causes
• Volcanic and human pollution aerosols net
  coolant to climate by reflecting sunlight.
  Volcanic CO2 production only 1 of
  human-generated CO2.
• Climate models (w/ high, low clouds, aerosols,
  volcanics, GHGs, deforestation, solar) agree
  closely with observed global temps.
• Atmospheric CO2 is human-caused, as shown by
  C13/C12 ratio changes.
• Fossil fuel burning dominates climate forcing
• Sea level rises due to thermal expansion of
  warmer seawater, and (rapidly increasingly)
  melting land ice
• Deforestation removes carbon sequestering trees,
  altering carbon cycle equation.
• Methane as greenhouse gas forces climate at 1/4
  that of CO2. Methane levels have tripled from
  human activities, since the pre-industrial times.
• Night-time low temps are rising faster than are
  day-time maximum temperatures.
• Tropical deforestation goes mostly to cattle
  ranches to satisfy fast-food restaurant demand