Transcript global climate change

Human Impacts on Ecosystems
• 1. If you missed Friday’s test, see me about a makeup time, and put your poster on the table by the
window.
• 2. Pick up the handout.
• 3. For a sticker:
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What gas do producers mostly output?
What gas do producers mostly take in?
What gas do consumers output?
What gas do consumers take in?
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Homework
• Ecosystem threat research due Tuesday June 2.
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Objectives
• Be able to analyze changes in population size and
biodiversity resulting from pressures including:
• Climate change
• Human activity
• Introduction of non-native species
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Climate Change
• To understand the impact of
climate change on a
population or ecosystem, of
course, we first need to
understand climate change.
• Lots of hilarious
misconceptions out there
about what it is. Exhibit A to
the right.
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The World Has Warmed
Globally averaged, the planet is about 0.75°C warmer than it was in 1860, based
upon dozens of high-quality long records using thermometers worldwide, including
land and ocean.
Eleven of the last 12 years are among 12 warmest since 1850 in the global
average. How did it happen?
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GHGs
• Greenhouse
gases (GHGs)
are gases that
absorb and emit
thermal infrared
radiation.
• How many GHGs
do you know of
already?
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GHGs
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Greenhouse gases
(GHGs) are gases that
absorb and emit
thermal infrared
radiation.
Main GHGs: water
vapor, CO2, methane
(CH4), nitrous oxide
(N2O), ozone (O3), and
chlorofluorocarbons
(CFCs).
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The order I just
listed them in is
their order of how
abundant they are
under natural
circumstances.
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GHGs
• The greenhouse
effect is critical to the
planet. Water vapor
especially is the
reason why the
planet’s surface and
ocean temperatures
permit life.
• Without the
greenhouse effect,
the planet would be
extremely cold,
uninhabitable.
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GHGs
• But this is not to say
that the warmer a
planet gets, the more
habitable it is.
• Just look at poor
Venus and
Mercury.
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• At the moment, extra
greenhouse gases especially carbon
dioxide - are being
very rapidly added to
the atmosphere,
accelerating the
system outside of
normal ranges.
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GHGs
• On this graph from
NOAA, look at three
things in particular:
• 1) The ranges of CO2
• 2) The differences in
CO2 and temperature
between glacial and
interglacial periods
• 3) Are we in a glacial
or interglacial
period?
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Industrial revolution and the atmosphere
The current concentrations of key greenhouse gases,
and their rates of change, are unprecedented.
Carbon dioxide
Methane
Nitrous Oxide
Notice rates of change, and how CO2 goes higher than
anything on the previous graph.
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(ppmv)
350
Last Interglacial
Last Ice Age
Carbon Dioxide
300
250
200
[Adapted from Figure 6.3, ©IPCC 2007: WG1-AR4]
600
500
400
300
200
100
0
Thousands of Years Before Present
Humans are ‘forcing’ the system in a new way. CO2 increases are
mainly due to fossil fuel burning. CO2 has not been this high in
more than half a million years.
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Ice ages
are not
random.
They are
'forced'
(by
earth’s
orbital
clock….
changes
in the
sunlight
received).
Effects of Additional GHGs
• Grey zone: Normal temperature fluctuations due to
natural sources of GHGs only.
• Red line: Actual temperature data.
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Effects of Additional GHGs
• Grey zone: Temperature fluctuations due to human
(anthropogenic) sources of GHGs only.
• Red line: Actual temperature data.
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Effects of Additional GHGs
• Grey zone: Temperature fluctuations due to natural
sources of GHGs and anthropogenic GHG output.
• Red line: Actual temperature data.
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Effects of Additional GHGs
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• What do you notice
about the three graphs?
• Climate change is
occurring due to the
additive effects of
natural and humanattributed GHGs.
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Human and Natural Drivers of Climate Change
Carbon dioxide is
causing the bulk
of the forcing.
On average, CO2
remains more
than a hundred
years in the
atmosphere and
therefore affects
climate over long
time scales.
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Human and Natural Drivers of Climate Change
Carbon dioxide is
causing the bulk
of the forcing.
On average, it
lives more than a
hundred years in
the atmosphere
and therefore
affects climate
over long time
scales.
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Various
Warmings
Rising
atmospheric
temperature
Rising sea
level
Reductions in NH
snow cover
And oceans..
And upper
atmosphere….
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Paleoclimate Lines of Evidence
•Classic demonstration
of how science
demands creative
minds!
•How do we figure
out what the
temperatures on
Earth were in the
past?
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Paleoclimate Lines of Evidence
•Changes in
glaciers, indicating a
global average
temperature change
in the 20th century
consistent with the
thermometers. And
the corals. And the
tree rings. And the
boreholes. And the
ice cores.
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Global distribution of
temperature change
for June/July/Aug
since 1880
http://www.ncdc.noaa.gov/gcag/gcag.html
•Notice: “global
warming” does not
equal “everywhere’s
warmer,” it equals
“most places are
warmer so the whole
thing is warmer on
average.”
This is one reason
why it’s more properly
termed “climate
change” than “global
warming.”
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Land Precipitation is changing significantly over broad areas
Smoothed annual anomalies for precipitation (%) over land from 1900 to
2005; other regions are dominated by variability.
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Effects on Matter Cycles, Too
Many dry areas are getting drier as soils dry
out.
Observed sea surface temperature (SST)
and links to the pattern of rain in Africa.
Sahara getting very large very fast: gaining
1.5 million hectares in the Southward
direction every year.
The matter cycles are intertwined; changing
one easily changes another.
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Sahelian rainfall decline
Anthropogenic
warming affects
some locations
more than
others, but
overall trend?
Observed
Expected for all
forcings
Natural forcing
only
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Changing winds, temperatures
and storm tracks
• Anthropogenic forcing
contributes to circulation
changes (storm tracks,
winds and temperature
patterns)
• Warmer, wetter winters
in Norway; drier in Spain
(and North Africa)
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Effects of Climate Change
• Effects
depend on
latitude
and
longitude,
but also on
elevation.
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Effects on Ecosystems
• Ecosystems fluctuate along with their environments,
so why can’t ecosystems just adapt to global climate
change?
• 1) Their ability to adapt to anything, anthropogenic or
natural, is severely hampered now by novel
destructions: mining, dams, pollution, habitat
destruction, poaching, overfishing, dragging, etc.
• 2) Rate of change. Species are always in the process of
shifting, but there’s a limit on how quickly they can do it.
Some are faster than others, so to determine the
survival of a system, you need to look at the slowest
members. These are usually, as it turns out, the
essential producers.
• Plants can migrate .4-2 km/yr. Surface temperature
changes are causing shifts at 1.5-5 km/yr.
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Effects on Ecosystems
• What could be the effects on ecosystems of
• Changes in temperature, including longer or shorter
warm/cold seasons
• Change in precipitation
• Change in groundwater available
• Change in sea level
• Change in sea acidity
• Change in winds and storms
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No names on: Madagascar Mangrove, Intertidal Zone
Global Climate Change
• For a sticker:
• 1. What is the most common GHG found naturally,
and which is the primary GHG being rapidly added to
the atmosphere?
• 2. What is the difference between these three
graphs?
• 3. What is one change or effect of an increase in
average temperature?
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Homework
• 1. Ecosystem Threat research due Tuesday
• 2. Test+ due Thursday
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Global Climate Change
• Inconvenient Truth: We’re not going to watch the
whole thing, no time. Picking out the parts with
especially nice graphs, and impacts on ecology.
• As you watch, keep in mind the various impacts on
an ecosystem we brainstormed a moment ago, and
consider which of them links to whichever part of the
system is onscreen at the moment.
• Ch. 3, 6-9, 11-12, 16-17, 19-21
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Global Climate Change
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Homework
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Objectives
• Be able to analyze changes in population size and
biodiversity resulting from pressures including:
• Climate change
• Human activity
• Introduction of non-native species
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Impact on Ecosystems
• Packet contains information about some ecology
studies in the last couple of years. Here is what I
want you to do:
• You’ll get into a group of 5-6.
• You don’t have to read all of the articles, pick 3 that
you’d like to have a closer look at.
• Read each one together, discuss to make sure everyone
in the group understands the study, then make a food
web of the ecosystem in question.
• Use your knowledge, the articles far from discuss
each organism in the web.
• Use another color to predict what changes are occurring
to the web. You will turn your three predictive webs in.
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What’s in the pipeline and what could come
Warming will increase if GHG increase. If GHG were kept fixed at
current levels, a committed 0.6°C of further warming would be
expected by 2100. More warming would accompany more emission.
CO2 Eq
3.4oC = 6.1oF
850
2.8oC = 5.0oF
600
1.8oC = 3.2oF
0.6oC = 1.0oF
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400
A1B is a typical “business as usual” (2090-2099)
scenario: Global mean warming 2.8oC;
Much of land area warms by ~3.5oC
Arctic warms by ~7oC; would be less for less emission
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Projections of Future Changes in Climate
New in AR4: Drying in much of the subtropics, more rain in
higher latitudes, continuing the broad pattern of rainfall
changes already observed.
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What else happens in a hotter world?
Observations of sea level rise from
satellites, 1993-2003.
The global average SLR for the 20th
century was about 6 inches (0.17m),
mostly from expansion of the hot ocean,
and with contributions from glacier melt
(Alaska, Patagonia, Europe….).
Future changes just from these
processes could be up to 1.5 feet
(0.5 m) by 2100, and up to 3 feet (1
meter) within about 2-3 centuries,
depending on how much GHGs are
emitted.
But what about other processes?
Rapid ice flow?
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Ice shelves influence glacier flow
The break up of the
Larsen B ice shelf off the
Antarctic Peninsula in
February 2002 is
illustrative of the speed up
of glaciers after the
blocking of the ice shelf is
removed.
Glaciers
lost ice
shelf and
sped up
Other examples, such
as Jakobshavn Glacier
(Greenland), show
speed up in flow after
collapse of the floating Glacier still has
ice shelf and did
glacier tongue.
not speed up
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[Image courtesy of
http://nsidc.org/iceshelves/larsenb2002/]
Sea level rise and the ice
sheets
7m of SL equivalent is on Greenland. This is
expected to melt slowly, and raise sea level
on a time scale of millennia, for warming
>2-5°C.
BUT rapid ice flow has been observed - and is
not in current models. Could sea level rise
be much faster than thought? Some
glaciological studies suggest this is
transient and will stop. Others suggest it
may increase.
Future?
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Past Change in The Greenland Ice Sheet
The last time polar regions were
significantly warmer (by 3-5°C)
than present for an extended
period (about 125,000 years
ago), reductions in polar ice
volume led to 4 to 6 m of sea
level rise.
White and black dots show drill
sites where ice older than
125,000 years is and is not
found.
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The IPCC Sequence of Key Findings……
IPCC (1990) Broad overview of climate change science,
discussion of uncertainties and evidence for warming.
IPCC (1995) “The balance of evidence suggests a
discernible human influence on global climate.”
IPCC (2001) “Most of the warming of the past 50 years is
likely (>66%) to be attributable to human activities.”
IPCC (2007) “Warming is unequivocal, and most of the
warming of the past 50 years is very likely (90%) due to
increases in greenhouse gases.”
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And More….
• Forcing: Greenhouse gases are at unprecedented levels,
and are forcing the climate to change.
• Beyond global warming: Discernible human influences on
other aspects of climate including heat waves, wind patterns,
drought, and more…this is the first ‘earth system’ IPCC report.
• Commitment: Already committed to more warming (next few
decades), with choices about emissions affecting the longer
term more and more.
• Expected future earth system changes: likely to virtually
certain: more extremes, wet in some places, dry in others, etc...
• Long term: Sea level rise is inexorable and will continue, and
the face of the planet will change. By how much? How fast?
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Water Vapor Feedback
Water vapor responds to
changes in climate, but it
doesn’t drive changes in
climate. It’s a major
feedback that amplifies
global climate change.
New in IPCC (2007):
Observed trends that
demonstrate the trend, in
both the upper
troposphere and at the
surface.
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Explosive Volcanic
Eruptions: Proof of
Fast-Response Climate
Change Due to Forcing
Changing forcing
changes the
temperature (and
water vapor, etc.).
If volcanoes can cool,
then GHG must
warm….
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Ice Age Forcing and Response
Last
interglacial
[After Figure 6.3, ©IPCC 2007: WG1-AR4]
Last
Ice
age
A different world in the Arctic: present and future
The Arctic was also warm in the period
1925-1940, but the extent of warmth was
not global at that time.
Large future changes in Arctic sea ice are
very likely.
Changes in sea ice don’t significantly affect
sea level because this ice is already
floating. Changes in land ice (glaciers, ice
caps, and ice sheets) do affect sea level.
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Clear decreases in Arctic
sea ice extent.
Could it be changes from the sun?
Afraid not. (Thankfully, actually. If it were the sun, there would be nothing
we could do about it….)
a) no observed trend in solar irradiance; b) spectral information c)
solar magnetic flux model rather than proxy data; d) re-evaluation of
variations in Sun-like stars.
No observed trend in this data. Solar forcing much less than greenhouse
gases. Hypothesis fell out of favor a couple decades ago.
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Solar
Attribution studies
• Separate time-space
patterns of response.
•
Solar response has very
different behavior to
greenhouse gases,
especially with altitude.
The upper atmosphere
would be expected to be
much warmer than it is if
solar irradiance were the
cause of current surface
climate change.
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“All” forcings