Summary Sustainability and Climate Risk GARP SCR 2023 Notes
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Sustainability and Climate Risk GARP SCR 2023
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Sustainability And Climate Risk GARP SCR 2023
GARP SCR tests your knowledge in much detail. You need to remember a variety of concepts and terms. The material needs multiple revisions. Reading the whol e text will be boring. This summary notes covers every item yet is much easy to read. You can even brush up with these notes in the last few da...
,I. I. FOUNDATIONS OF CLIMATE CHANGE: WHAT IS CLIMATE CHANGE
● Define climate change and differentiate between weather and climate.
● General trends of modern climate change.
● How earth’s climate has changed over long periods of time and different methods for measuring non-
anthropogenic climatic changes at different time frames.
● How the earth’s energy balance, green-house effect, and radiative forcing affect the climate.
● Primary greenhouse gases and aerosols, their sources, and relative contribution to climate change.
● Greenhouse gas global warming potentials as well as atmospheric lifetimes.
● How humans have contributed to atmospheric CO2 increases and modern warming.
● Distribution, frequency, and intensity of climate driven economic and ecological impacts across geography
and time.
● Contributors to and risks from, sea level rise and ocean acidification.
● Extreme event attribution science and the data and techniques scientists use to connect climate change to
extreme events.
● How positive feedbacks influence climate change.
● How climate tipping points could disrupt natural systems and harm human well-being.
● Climate change adaptation, including maladaptation.
● Trends in the energy system and how energy sources can contribute to or mitigate climate change.
● Relative carbon intensities of energy sources.
● Opportunities and strategies for renewable and low emissions energy technology to act as climate mitigants.
Challenges (e.g., intermittency) in deploying each technology.
● The opportunities and drawbacks of implementing geoengineering techniques to combat climate change.
● Carbon budgets and emissions trajectories to stay within mitigation targets. Key numeric global emissions
limits, commitments, and scenario paths.
Introduction
● Weather refers to the exact state of the atmosphere at a particular location and time.
● Climate refers to long term patterns or statistics of the weather.
● Climate usually refers to temperature but has other parameters, precipitation, humidity, cloudiness, visibility
and wind.
● Climate is estimated from the statistics of weather over a period of several decades, usually 30 years.
OBSERVATIONS OF CLIMATE CHANGE
1.1 Modern Climate Change
● Surface thermometer record shows that the earth has warmed by 1.1 degree centigrade during the past
150 years that observations have been taken.
● The warming is not uniform- land has warmed more than the ocean and the northern hemisphere
warmed more than the tropics or the southern hemisphere.
● About 93% of the heat trapped by greenhouse gases goes into heating the oceans.
● Recent reports from the Intergovernmental panel on climate change (IPCC) have described the
confidence in the warming of the climate since the early 20th century as unequivocal meaning beyond doubt.
Other evidence of Global Warming: -
➢ Ice on planet is disappearing.
➢ Sea level is rising (contributed by melting ice and water expanding when heated)
1.2 Climate change before Humans
Measurements of temp change go back 170 years, so to look back further we use geological chemical or
biological systems that store information.
(i) Tree rings- trees grow more in warm and wet years to produce warmer rings;
(ii) Corals: analysis of skeletons give info for millions of years
(iii) Speleothems e.g. stalactites & stalagmites: information on climate for few thousand years.
(iv) Ice Cores: Chemical composition (Greenland & Antarctica) info for million years.
(v) Ocean Sediment cores: mud at the bottom of ocean gives information of tens of millions of years.
, Historical temp
⮚ 50 million years ago: earth was much warmer and had no permanent ice.
⮚ Last 400 thousand years: earth has been cycling between cold periods (ice age) and interglacials (warmer
periods) cycle of about 100000 years.
⮚ Last ice age: about 20000 years ago and ended 10000 years ago.
⮚ Holocene: since last ice age of 11000 years
⮚ 7000 years ago: temperature peaked and had a slow and steady decline and bottomed about 200/300
years ago known as little ice age.
⮚ Global average temp diff between ice age and interglacial is about 6° C.
⮚ Average warming now 1°during last century is 16 times faster than rate coming out of last ice age (roughly
6° C in 10K years or 0.06°C /Century)
CAUSES OF CLIMATE CHANGE
1.3 Energy Balance
Source of earths energy is sunlight which provides 340W/m2 (annual average)
30% of this is reflected back since all heated bodies radiate energy (determined by temp of the object);
Energy Balance: For a given amt of energy from sun, there is a temperature of the planet that will give back equal
amt of energy radiated back.
1.4 The Greenhouse effect
⮚ Apart from temperature of the earth the composition of its atmosphere determines how much energy is
radiated back. Greenhouse gases absorb infrared radiation.
⮚ Nitrogen, oxygen and inert gas Argon forming the majority do not absorb heat. The main greenhouse gases
are Water vapour (traps most heat), CO2 (415 ppm or 0.0415%) and other gases like methane.
⮚
1.5 How Humans are changing the climate
1.5.1 Carbon Dioxide
Since 1960 CO2 increased from 320 ppm to 415 ppm. Plotted on a curve called Keeling Curve. Primary reason for
increase is burning of fossil fuels. This fact is supported by multiple data sources-
(i) CO2 began increasing at beginning of 19th century i.e. same time we started using lot of fossil fuels;
(ii) for the past 50 years CO2 increase averages 44% of what humans released in atmosphere in that year; of the
56% that is removed half is absorbed in the Oceans leading to Ocean acidification and other half by plants;
(iii) chemical composition of CO2 released has an isotope composition consistent with CO2 from fossil fuels.
(iv) Air bubbles in glacial ice provide info that before industrial revolution there was 280 ppm of CO2.
1.5.2 Other Greenhouse gases and aerosols
After water vapour and CO2 the next important gas is methane which increased from 0.8 ppm before industrial
revolution to 1.9 ppm in 2020. Each kilogram of methane traps as much heat as 28 kilograms of carbon dioxide.
This heat-trapping power relative to carbon dioxide is known as the global warming potential (GWP). Other
powerful greenhouse gases are nitrous oxide (N2O) and an entire class of molecules called halo-carbons.
Ozone (O3): This molecule is best known for its ability to absorb ultraviolet radiation that, but it is also a powerful
greenhouse gas. Humans do not directly emit ozone into the atmosphere, but they emit ozone’s precursors
(hydrocarbons and oxides of nitrogen), which react in the atmosphere to form ozone.
Aerosols: Another way that humans are changing the climate is through emissions of aerosols or their precursors.
Aerosols are small particles that can remain suspended in air, and they reflect incoming solar radiation back to
space, so their net effect is to cool the climate.
Burning of fossil fuels can produce sulphur which is an aerosol.
, 1.5.3 Summarizing The Human Impact on Our Climate
Water vapor is not directly affected by human activities as it depends on earth temperature.
Water vapor feedback: A warmer atmosphere can hold more water vapor. Thus, an initial warming leads to
increased atmospheric humidity, and because water vapor is itself a greenhouse gas, this leads to additional
warming, and that feeds back to increase the humidity.
1.6 Attribution of Modern warming
Mechanisms that are known to change the climate and evidence of human influence for each:-
(1) Tectonic processes: The Earth’s continents are moving and this continental drift can substantially alter the
arrangement of the continents across the Earth’s surface. Movement of a continent toward the poles can lead
to the growth of an ice sheet on the continent. Because ice sheets are reflective, the growth of a continental
ice sheet will lead to more incident sunlight being reflected back to space, which will tend to cool the climate.
However, this process is exceedingly slow— millions of years.
(2) Output of the Sun: The observed warming trend could be explained if the Sun had been getting brighter
over the past two centuries but there is no long-term trend that could explain the very rapid warming over that
period.
(3) Orbital variations: The amount of solar energy reaching the Earth is affected by the Earth–Sun distance.
The date of closest approach of the Earth to the Sun, presently occurring in January, cycles through the calendar
over a period of about 23,000 years. These variations are responsible for the ice ages but could not be the cause
of modern warming because the orbit does not change much over a century.
(4) Unforced variability: Earth’s climate system is so complex that it can also vary without an imposed energy
imbalance. Such changes, which are caused by complex internal physics of the climate system, are often referred
to as unforced variability. The best-known example of unforced variability is the El Niño/Southern Oscillation
(ENSO). El Niño events, the warm phase of ENSO, occur every few years and last a year or so, and alternate with
cooler La Niña events. But this cannot be reason for earth warming because (i) no theory can explain the observed
warming since the industrial revolution (ii) observations of the past millennium show nothing similar to the rate
and magnitude of warming of the twentieth century (iii) computer simulations of the climate do not support this
as a cause.
(5) Greenhouse gases: Physics tells us that adding carbon dioxide, or any other gas that absorbs infrared
radiation, to the atmosphere should warm the planet by affecting the planet’s energy balance. Second, it is a fact
that humans are adding carbon dioxide to the atmosphere. Finally, the geologic record shows that changes in
climate are frequently associated with changes in greenhouse gases. For example, carbon dioxide changes during
ice-age
cycles are thought to play a key role in amplifying the size of the climate variations.
1.7 Summary statement on Attribution of Modern warming
The Sixth Assessment Report (AR6) of the Intergovernmental Panel on Climate Change, published in 2021, came
to the following conclusion:
It is unequivocal that human influence has warmed the atmosphere, ocean, and land. Widespread and rapid
changes in the atmosphere, ocean, cryosphere, and biosphere have occurred. Thus, it is beyond doubt that
humans are warming the climate system.
The likely (confidence of 66%.) range of total human caused global surface temperature increase from 1850–
1900 to 2010–2019 is 0.8°C to 1.3°C, with a best estimate of 1.07°C.
Because the observed warming over this period is about 1.1°C, the best estimate is that humans are responsible
for 100% of the observed warming of the climate system.
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