Global Climate Change

P. Brian Fisher

College of CharlestonPOLS 405

Class 1: Climate Change Primer

Earth’s Limits

“Moreover, we are fast approaching many of earth’s limits. Current economic practices that damage the environment, in both developed and underdeveloped nations, cannot be continued without the risk that vital global systems will be damaged beyond repair”

--GEG, pp. 14-5 (from Natural Resources Journal 2001)

“The earth is finite. Its ability to absorb waste and destructive effluents is finite. Its ability to provide food and energy is finite. Its ability to provide for growing numbers of people is finite…”

Kiribati Video

• Life on the Edge: The President’s Dilemma

Affecting Climate?

Definitions• Climate Change: long term change to earth’s climatic

system—not necessarily uniform or equal

• Global Warming: Increases in global mean temperature

• Weather: all phenomenon in earth’s atmosphere at a given time (e.g. temperature, precip, etc.).

• Radiative forcing: essentially, the difference between the incoming radiation energy and the outgoing radiation energy in a given climate system, measured in Watts per square meter. – Use by the IPCC: changes in climate from changes in earth’s

energy budget

• IPCC: Intergovernmental Panel on Climate Change

IPCC: Unequivocal Warming

“Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level”

Global Warming• Global Mean Temp: 1.5°F increase in average global

surface temperature in the past century.

• Rate Increase: The rate of this increased warming has accelerated as the warming over the last fifty years is 0.13°C, almost double for the previous 50 years, and this rate has increased to 0.17°C per decade in the last twenty-five years.

• SOUTHEAST US: Since 1970 annual avg temperature has risen about 2°F (greatest increase in winter). The annual # of freezing days has declined by four to seven days for most of the region. 

Global Warming, IPCC Findings• Eleven of the twelve years in the period (1995-2006) rank

among the top 12 warmest years in the instrumental record (since 1850).

• Urban heat island effects were determined to have negligible influence (less than 0.0006 °C per decade over land and zero over oceans) on these measurements.

• "Average Arctic temperatures increased at almost twice the global average rate in the past 100 years."

• It is likely that greenhouse gases would have caused more warming than we have observed if not for the cooling effects of volcanic and human-caused aerosols.

• “Warming in the last 100 years has caused about a 0.74 °C increase in global average temperature.” (up to 2007)

Observed Changes in Climate• SLR (sea level rise) is consistent with warming. Global average SLR

has risen about 2mm/yr since 1961 and is accelerating (now at 3.1mm/yr since 1993)

• Decreases in Ice and snow are also consistent with warming. Avg Arctic sea ice has shrunk 2.7% per decade, with larger decreases in Summer 7.4% per decade

• Mtn glaciers and snow cover have declined in both hemispheres

• Lengthening growing seasons (northern hemisphere) and shifting biodiversity (moving to higher altitudes)

• Mean global sea surface temp (SST) of oceans have warmed from 0.10°C (1961 to 2003), with some estimates of SST are higher, suggesting a 0.31°C increase since 1950.

Global Effects from GCC1. Ice Melt/Deglaciation2. Rising sea levels (ice melt, increase in water)3. Changes in extremes of temperature4. Salination of Water and Soil5. Increase in Extreme weather (storm surges,

precipitation, hurricane/cyclone intensity)6. Changes in Wind patterns and intensity7. Wind and SLR lead to coastal erosion8. Droughts and flooding9. Increase in Ocean temperature10. Increase in insects (particularly mosquitoes)11. Changes to growing seasons

3 Ways to Change Climate

There are three fundamental ways to change the radiation balance of the Earth:

1) by changing the incoming solar radiation (e.g., by changes in Earth’s orbit or in the Sun itself);

2) by changing the fraction of solar radiation that is reflected (called ‘albedo’; e.g., by changes in cloud cover, atmospheric particles or vegetation); and

3) by altering the longwave radiation from Earth back towards space (e.g., by changing greenhouse gas concentrations).

Climate, in turn, responds directly to such changes, as well as indirectly, through a variety of feedback mechanisms."

Anthropogenic Climate Change

Fingerprint-modeling of global surface temperature change (Adapted from Meehl et al. 2004). (A) Model results with all forcings included. The combined forcings provided the best match to the fingerprint of climate change in the observed record. (B) Natural forcings alone explained much of the temperature change in the first half of the century. (C) Man-made forcings strongly dominated the temperature change after 1975.

Note: The 20th C warming trend at the earth’s surface progressed in a distinct pattern, with a large warming during 1910-1940, moderate cooling during 1940-1975, and a large warming from 1975 to today.

GHG Emissions (∆CO2; ∆CH4; ∆N2O; ∆ HCs)

Anthropogenic Drivers

(human activities)

Atmospheric Concentrations:“Climate Drivers”

(GHGs, aerosols, clouds, solar irradiance)

Radiative Forcing

(GWP Metric)

BiophysicalClimate

Responses(global/regional ∆ temps & ∆ precip, ∆ vegetation, extreme

weather)

Increasing Uncertainty

Biogeochemical Feedback

Biophysical Climate Cycle

Natural Drivers(solar processes,

earth’s orbit, volcanoes)

Biophysical Climate Change Process

Anthropogenic drivers augment natural levels of GHGs and together with natural processes trigger climate drivers (e.g. clouds, GHG concentrations). These changes result in specific radiative forcing, positive or negative (along with some non-radiative effects like evaporation). This radiative forcing then creates biophysical responses in the climate system, such as changes to regional or global temperature and precipitation, and extreme weather events. Biogeochemical processes then operate as feedbacks from climate change back to its drivers. Finally, with each step further into the process, there is greater scientific uncertainty.

Ice reflects solar radiation very well; water absorbs most of it. So if you have some of the ice melt and it is replaced by water, then there is a lot less radiation being reflected back because you have replaced the albedo of ice with the albedo of water. That means more absorption, and tends to warm up where the ice is melting.

NOT Solar Output/Irradiance

• Since 1750, the average amount of energy coming from the Sun either remained constant or increased slightly. Since 1978, with actual measurements, show decrease in activity

• If the warming were caused by a more active sun, then scientists would expect to see warmer temperatures in all layers of the atmosphere. Instead, they have observed a cooling in the upper atmosphere, and a warming at the surface and in the lower parts of the atmosphere. That's because GHGs are trapping heat in the lower atmosphere.

• Climate models that include solar irradiance changes can’t reproduce the observed temperature trend over the past century or more without including a rise in GHGs.

• NASA Warming Climate Explained

Not Natural Cycles• Earth’s atmosphere has indeed gone through many

changes in climate over its 4.5b history

• Natural cycles are created in earth’s climate from earth’s orbit, tilt (21.8-24.4°), and its axis rotation (precession).

• Earth’s orbit (eccentricity) operates in 100k cycles which roughly mirrors the cycles of ice ages

• Many factors suggest we should be cooling from natural cycles not warming

• **If warming from natural cycles, we’d expect daytime temps to represent much of the increase (more solar radiation), but we see more increase in nighttime temps

Feedbacks mechanisms, such as albedo, play a major role in driving climate change. The reflectivity of various surfaces is shown on the chart (right side) above. The seasonal and annual changes in the earth’s northern hemisphere albedo are shown on the image above (100% reflectivity is denoted as 1.0 on the scale). The two images on the lower right are infrared satellite images of Lake Tahoe, CA taken during winter (left) versus late spring (right).

Albedo 0-1 (0=no reflection) on Multi-Angle Imaging SpectroRadiometer

See: eosweb.larc.nasa.org/HPDOCS/misr/misr_html/global_seasonal_albedo.html

Causes of GCC(IPCC 2007)

• Global GHG emissions (from human activities) have exploded with an increase of 70% just since 1970. Humans pump 30 million metric tons of CO2 into atmosphere every year. 2% increase every year, and double CO2 every 30 years.

• “Carbon dioxide is the most important anthropogenic greenhouse gas (see Figure SPM.2). The global atmospheric concentration of carbon dioxide has increased from a pre-industrial value of about 280 ppm to 379 ppm in 2005.”

– 387 ppm (July 2009); 390 (Dec 2010). See CO2 Now

• “The primary source of the increased atmospheric concentration of carbon dioxide since the pre-industrial period results from fossil fuel use, with land-use change providing another significant but smaller contribution.”

• Methane and Nitrous Oxide have both increased significantly, and current levels “far exceed any previous levels for last 650,000 yrs.”

• The combined radiative forcing due to increases in carbon dioxide, methane, and nitrous oxide is +2.30 [+2.07 to +2.53] W m–2, and its rate of increase during the industrial era is very likely to have been unprecedented in more than 10,000 years

• The understanding of anthropogenic warming and cooling influences on climate has improved, leading to very high confidence that the global average net effect of human activities since 1750 has been one of warming

Main Greenhouse Gases (GHGs)

• Carbon Dioxide (CO2)– Steady at 270ppm until Ind Rev

• Methane (CH4) – 1/3 impact of CO2

• Nitrous Oxide (N2O)

• Ozone (O3)

• Water Vapor (largest part)

GHG Emissions Flow Chart

GWP (Global Warming Potential)• ( concentration ) X ( the appropriate GWP multiplier

(2) (3) of each gas relative to CO2 ) = GWP• CFCs banned (Montreal Protocol) substituted HFCs

which do contribute to GW

% of GHGs % Rise since 1750 Sources Time in Atmosphere GWP

Carbon (CO2) ~63% ~ 31% Autos, fossil fuels,

deforestation

100-200 years 1

Methane (CH4) ~ 18% ~ 151% Livestock, rice, landfills, coal

mining

12 years +-3 yrs 25

Nitrous Oxide (N2O) ~ 6% ~17% Auto exhaust, fertilizers, waste

120 years 300

Flourocarbons (CFCs; HFCs)

~ 12% Rising sharply AC, Fridge Varies(CFC11-12: 45-100 yrs)

~1k-22k

Atmospheric CO2 concentrations

Charles Keeling

Mauna Loa, Hawaii

CO2 Concentrations (Mauna Loa)

IPCC Findings, Industrial Revolution

“Global atmospheric concentrations of carbon dioxide, methane and nitrous oxide have increased markedly as a result of human activities since 1750 and now far exceed pre-industrial values”

Proxies for Evaluating Climate

How do we establish long-term assessments of climate change?

1. Temperature records

2. Tree Rings

3. Ice Core Samples

4. Sediment samples

5. Observations/Traditional Knowledge

Findings, IPCC (2007)

The amount of carbon dioxide in the atmosphere in 2007 (385 ppm) exceeds by far the natural range of the last 650,000 years (180 to 300 ppm).

Co2 over last 400k years

Figure 4

Barnola et al.

Al Gore Explains ”temperature changes”

Projected Increases in Global Temperature

• NASA 2009 Video on Warming

• Climate Modeling (NASA)

• Global projections on Temperature (1974-2099)

Projected surface temperature changes for the early and late 21st century relative to the period 1980–1999. The central and right panels show the Atmosphere-Ocean General Circulation multi-Model average projections for the B1 (top), A1B (middle) and A2 (bottom) SRES scenarios averaged over decades 2020–2029 (center) and 2090–2099 (right). The left panel shows corresponding uncertainties as the relative probabilities of estimated global average warming from several different AOGCM and EMICs studies for the same periods. Some studies present results only for a subset of the SRES scenarios, or for various model versions. Therefore the difference in the number of curves, shown in the lefthand panels, is due only to differences in the availability of results.

Temperature Projections in 2100 (A1B)

Peak Temp in Southeast US

SLR: New Projections

New studies find that warmer temperatures and changes in precipitation caused by CO2 emissions from human activity are largely irreversible. Atmospheric temperatures are not expected to decrease for many centuries to millennia, even after human-induced greenhouse gas emissions stop completely (Solomon et al. 2009; Eby et al. 2009).

New Findings Since IPCC 2007• The link between fossil fuel emissions and GCC is

increasingly clear• Ocean acidification severely threatens marine

ecosystems and fisheries• Better understanding of ice sheets has raised

projections of 21st C global SLR• Surface melting of the Greenland Ice Sheet is

accelerating & Arctic sea ice and permafrost melting more rapidly than projections

• Antarctic ice shelves are collapsing more rapidly than expected

• Warming will be higher than IPCC projections (based on current emissions trends)

Main Features of GCC1. Human Induced: current climate changes are largely human caused

2. Positive Feedbacks: thermal expansion, lessening albedo, and increasing melting, increasing water vapor, all feedback into system accelerating GCC

3. Climate variability: both at different spatial and temporal scales, which often leads to climate extremes.

4. Local/Regional Phenomenon: because of variability, GCC is best characterized as a regional or local phenomenon.

5. Inertia: The GHGs all have half-lives that will keep them in the atmosphere from 10-1000+ years.

6. Adaptation is necessary. Because of inertia, climate effects will continue for centuries and adaption is needed even if stopped today

7. Irreversible: GCC is irreversible.

8. Poor Most Affected: The impoverished areas, those more dependent on natural resources, will be most affected (Injustice??)

UNFCCC and Kyoto Protocol• UNFCCC: United Nations Framework

Convention on Climate Change– US signed ratified.– Core framework int’l agr on GCC

• Kyoto Protocol– Addendum to UNFCCC– Calls for developed countries to limit their GHG

emissions by certain dates.– Full compliance would “only make a small dent in the

world’s ever-increasing output of GHGs.” (RG)

• Copenhagen and Cancun