fundamentals of climate Flashcards
lectures
what are the components of the climate system?
atmosphere
ocean - including its biosphere
land - including its biosphere
cryosphere - glaciers, ice caps, sea-ice, seasonal snow cover
koppen climate classification determines variation of climate with location and is broadly determined by….
latitude, altitude, disatnce from the ocean, seasonal variation of temp and rainfall
temperature falls strongly with height in the…
troposphere and increases again in the statosphere
what temperature emits radiative energy?
absolute 0 (0 K or -273 degrees celsius) which includes ME!
what is the perfect emitter of radiation called?
a black body
what is total energy of the sun emitted per second per metere-squared?
T~5800 K
how much energy do we emit? (T - K measurement units )
T~300 K
What are good emitters and absorbers of thermal infrared radiation?
clouds and many gases in the atmosphere such as CO2 OR H2O
what amount of energy is available to warm the earth and power the earths system?
340 W m-2
what amount of sun is reaching the earth? (totar solar irradiance - w m-2)
The amount reaching the Earth is called the “Total Solar Irradiance” So ≈ 1360 W m-2
is all of the suns energy absorbed by the earth and if no where does it go?
Not all this energy is absorbed by the Earth. Satellite observations show that 30% of it is reflected back to space by clouds (≈15%), the Earth’s surface (≈10%) and atmospheric gases (≈5%)
what is the 30 percent of energy which is not absorbed by the earth and is reflected back to space by clouds, the earths surface and atmospheric gases known as?
planetary albedo - normally given as a decimal fraction, 0.3
what amount of energy is absorbed by planet earth? (W m-2)
240 W m-2
where is the earths emission and why?
in the thermal infrared - because its relatively cold
what percent of what is emitted by the surface reaches space?
60 percent
This is because greenhouse gases and clouds absorb the infrared radiation emitted by the surface; because the atmosphere is cooler than the surface, the amount it emits is less than the amount it absorbs
And some of the atmospheric emission is down to the surface, which helps keep the surface warm
how much of the suns energy reaches the surface?(fraction ish number)
around two-thirds
– the role of the greenhouse gases is to essentially “trap” that energy in the system, keeping the surface warmer than it otherwise would be
atmosphere is made up of 99 percent of..
nitrogen and oxygen
These are simple molecules that are ineffective at absorbing thermal infrared radiation
which main greenhouse gases are responsible for the natural greenhouse effect?
h20 - 60 percnt
co2 25 percent
other gases…..ozone, methane nitrous oxide
what percent do clouds contribute of trapping thermal infrared radiation?
around 20percent
which parameters determine the earths energy balance?(3 things)
the total solar irradiance , the planetary albedo and the concentrations of greenhouse gases, such as CO2
If any of these change they lead to an imbalance in the Earth’s energy budget (called “radiative forcing” – see next week) and the climate system responds (“climate change”) to try to re-establish balance
what is an imbalance in the earths energy budget called
radiative forcing
signs of radiative forcing determine whether the climate system….
warms or cools
changes in components of the climate system which influence the earths energy budget are called..
feedbacks
what do feedbacks do?
they can either amplify or reduce the size of climate change
feedbacks + radiative forcing - determine …
how large climate change is
water vapour (powerful greenhouse gas) is expected to increase by…
7 percent for every degree warming - A POSITIVE FEEDBACK
snow and ice in a warming world are expected to ….
decrease the planetary albedo - a POSITIVE FEEDBACK
what is one of the biggest uncertainties in climate change?
how clouds respond to climate change? - probably a positive feedback
positive feedback…
either speeds up or slows down a warming trend
different types of observations include..
direct - temp
remotely sensed- satellites
proxy and paleo - ice cores, tree rings
re analyses sophisticated combo of observations and weather forecast models
issues in measuring climate variables such as precipitation and temperature include…
consistency
continuity of measurement method
spatial variability - how many observations are needed to build a reliable pic
observation systems were often designed for providing data for weather forecasting…… this matters because?
there are various potential pitfalls in using data for climate trends…. SCEPTICISM when you see this!
sea surface temperature measurement methods used include…
buckets
measuring temp of water used to cool ship engines
recently - satellite observations
issues with satellites….
short lifespan
passing over the same spot different times of the day - makes it difficult to compare data
joining records together with sellotape
IPCC LANGUAGE….
“Virtually certain” = greater than 99% chance that the result is true
· “Very likely” = 90 – 99% chance
· “Likely” = 66 – 90% chance
· “Medium likelihood” = 33-66% chance
· “Unlikely” = 10-33% chance
· “Very unlikely” = 1-10% chance
· “Exceptionally unlikely” = less than 1% chance
how do scientists study ice cores?
Scientists can learn about Earth’s climate from the past by studying Antarctic ice cores, which are cylinders of ice drilled from deep within the ice sheets. These ice cores contain tiny air bubbles trapped within the ice, which provide a record of past atmospheric conditions.
One way scientists use ice cores is by measuring the concentration of carbon dioxide (CO2) trapped in these bubbles. By analyzing the air bubbles, scientists can estimate the levels of CO2 in the atmosphere going back nearly 1 million years. This helps us understand how CO2 levels have changed over time.
Another method involves studying the isotopic composition of water molecules in the ice cores. Different isotopes of water have slightly different weights, and the ratio of these isotopes can give scientists clues about past temperatures. By analyzing these isotopes, scientists can infer temperature variations over long periods.
how much has the earth warmed since the “pre-industrial” era?
1.2 degrees celsius
is land warming faster than the oceans?
yes
is the arctic warming faster than the rest of the globe?
yes
is the stratosphere cooling?
yes
why is the stratosphere cooling?
due to
ozone depletion
and
co2 increases
have hot extremes become more frequent and intense since 1950s?
yes
have cold extremes become less frequent and severe?
yes
is arctic sea ice at its lowest trend in the past 1000 years?
yes
how much is global sea level rise since the 1900
0.2 metres
what does ENSO stand for?
El Niño-Southern Oscillation,
During its positive phase, known as El Niño, ocean temperatures in the Pacific are warmer than usual. This can lead to….
various weather extremes globally, including storms, droughts, and floods.
a new el nino is starting…true false>
true
ipcc report human influence has warmed the atmosphere, ocean and land? true or false
true
what is the best estimate of human-caused global surface temperature increase? in degrees celcius
1.07 degrees celsius
since at least 1970s, there has been persistent imbalance in energy flows that has led to….
excess energy being absorbed by different components of the climate system
imbalanced energy is….
incoming solar energy and less outgoing energy due to greenhouse gases
a stable climate: in balance would consist of…
incoming solar energy and outgoing energy
forcing means..
Forcing refers to a disturbance or perturbation in the balance of energy in Earth’s atmosphere caused by external factors, such as changes in greenhouse gas concentrations.
forcing definition in simpler terms..
In simpler terms, forcing is like poking a delicate balance, such as a seesaw, causing it to tilt temporarily. In response, the climate system adjusts to bring things back into balance, which can lead to changes in temperature, weather patterns, and other aspects of Earth’s climate.
the Radiative Forcing due to observed CO2 increases (since 1750) due to human activity is about( w m-2) ..
2 W m-2.
Radiative forcing leads to ….
a temperature change as the climate system tries to re-establish planetary energy balance
resulting temperature change depends on ….
how big the radiative forcing is,
size of climate feedbacks
how long the radiative forcing is applied for
A 2 W m-2 forcing, if applied for a sufficiently long time, would cause a surface warming of about…
1.6oC
Uncertainties in the size of climate feedbacks, which determine the “climate sensitivity” means the “likely” range is about 1.2 to 2oC
climate drivers:
Greenhouse gases: carbon dioxide, methane, CFCs, ozone … more means warming
Tiny particles (“aerosols”): reflect or absorb sunlight; depending on their properties can cool or warm; very likely cool
Tiny particles: also modify cloud properties, making them reflect more sunlight; cool, possibly significantly
Others: e.g., forest farmland, aircraft contrails – mixed impacts but likely small
Natural changes: sun’s variations, volcanic eruptions … either warm or cool
Internal (unforced) variability (“chaos”): either warm or cool
We must rule out causes as well as rule in causes
changes in energy from the sum is a powerful driver of climate change. it can happen in two ways:
Changes in the amount of energy emitted by the Sun
Changes in the characteristics of the Earth’s orbit around the Sun
while changes in TSI might seem significant, the actual impact on Earth’s climate is smaller once factors like …
absorption and reflection are taken into account.
orbital parameters vary because of…
ellipse shape
tilt of the earths axis of rotation
timing we are closest to the sun occurs relative to the solstice
-By coincidence, we are in a period when the Earth’s orbit is close to being circular
why do orbital variations matter?
they affect the seasonal distribution of radiation
E.g., if maximum tilt occurs when we are closest to the Sun, the Arctic gets more intense sunlight.
“Milankovitch Effect” is a prime driver of ice ages - what it means….
means more winter snow and ice melt; glaciers and ice caps are less likely to form
At other times, glaciers and ice caps may be more likely to form
because of orbital variations which affect seasonal distribution of that radiation
Explosive volcanic eruption: sulphur gases reach the stratosphere and form ….
sulphate aerosol particles; lifetime of around a year.
what do sulphate aerosol particles cause?
negative forcing
planetary albedo means…
Think of planetary albedo as the “reflectivity” of the Earth’s surface. Just like how some materials reflect light while others absorb it, Earth’s surface reflects some of the sunlight that hits it back into space.
Planetary albedo is a measure of how much of the Sun’s energy that hits the Earth is reflected back into space, compared to how much is absorbed by the Earth. It’s like a fraction or percentage that tells us how “bright” or “shiny” Earth looks from space.
For example, if Earth had a planetary albedo of 0.3, it means that 30% of the sunlight that hits Earth is reflected back into space, while the remaining 70% is absorbed by the planet’s surface.
So, in simple terms, planetary albedo is like Earth’s “brightness factor” from space—it tells us how much sunlight gets bounced back versus how much gets soaked
Effusive volcanic eruptions: Sulphur gases and sulphate aerosol particles stay in …..
troposphere;
lifetime of ≈weeks. Little impact on climate
Climate impact of eruptions depends on ….
amount of stratospheric sulphate aerosol
The radiative forcing due to eruptions can be substantial (-2 W m-2) and have an observable effect on climate in the years immediately after it……
But the long-term effect of individual eruptions is small because of ….
the aerosol’s short lifetime compared to the climate response time – see earlier
what is the most dominant anthropogenic radiative forcing mechanism (2.2 W m-2)?
CO2
What are three major gases emitted by human activity what also occur naturally in the atmosphere?
CO2 CH4 AND N20 (NITROUS OXIDE)
what is methane sometimes referred to as?in terms of long or short
long-lived and sometimes as short-lived
is ozone o3 long lives or short lived?
classed as short-lived with tropospheric lifetimes of months
methane sources
fossil fuel extraction and anaerobic environments
methane lifetime?
around a decade
what do methane increases lead to?
tropospheric ozone increases
whats is the reason for recent methane growth rate?
could be increased anthropogenic sources
changes in its chemical destruction rate in the atmosphere
response of natural sources to climate change - feedback
what shows success of international environment treaties?
chlorofluorocarbons outlawed by UN Montreal protocol to protect the ozone layer so production and emissions are now very low
but long lives gases so concentrations only slowly decrease
what was chlorofluorocarbons eventually replaced with?
hydofluorocarbons
what is the most significant contributor to negative radiative forcing?
aerosols
what are aerosols
tiny particles emitted into the atmosphere by human activity or form in the atmosphere because of emissions of gases such as sulphur dioxide
what are 2 contributors to aerosol concentrations?
sulphates and black carbon (Soot)
when did sulphur concentrations peak?
in 1980s
are aerosols short lived or long
short - a few weeks lifetimes
what is aerosol-radiation interaction
the way aerosols affect incoming solar radiation
This depends on their size and their composition. Sulphate aerosols increase planetary albedo αp (by reflecting sunlight); black carbon aerosols decrease αp (by absorbing sunlight). The net effect is a negative forcing (i.e., increased αp)
what are volcanic aerosols and what is the lifetime?
volcanic emissions reaching the stratosphere and have a lifetime of a few years
aerosols are a a vital component in…
cloud formation
ipcc radiative forcing figure emphasises that the net effect of human activity is positive forcing from what years?
1750-2019
what percentage of emissions does methane contribute to
60 percent
in the past decade burning coal, oil and gas has added how many units of CO2 each year to the atmosphere?
5 units
what has removed half of the emitted c02
land and oceans! - great favour to us
fossil fuel emissions started to dominate after… what year?
1950s
what do model simulations indicate about the uptake of emitted c02? most of it is by …….. in the….
that most of it is by land in the tropics and mid- latitudes
ocean uptake of c02 is highest in the… (what ocean)
southern oceans
what country is the biggest c02 emitter
china
what are the percentages of countries historically responsible for emissions
Although China is the biggest current emitter, it is responsible for “only” 13% of all historical emissions. USA is responsible for 25%, EU27 for 17% and UK for 5%
what is the carbon budget?
i.e., how much CO2 we can emit to meet a given temperature target) …
this concept led to the concept of net zero
what does warming depend on…… what emissions? what gas?
the cumulative emissions of c02
how much c02 have we already emitted?
We have already emitted ≈2500 GtCO2; caused a warming of about 1.1 oC (Red)
to meet the 1.5 degree target how much more can we only emit now?
To be reasonably confident of meeting a 1.5 oC target, we can only emit ≈500 GtCO2 more (Blue) This is the remaining “carbon budget”
definition of net zero c02 emissions
IPCC defines this as the “… condition in which anthropogenic CO2 emissions are balanced globally by anthropogenic CO2 removals over a specified period”
we need to be NEAR net zero by what year?
2050
what is a strong hint from ice core record?
C02 is higher in warm period
the land and ocean will continue to take up much of the CO2 we emit, but……. what will make this less efficient?
but climate change will make this uptake less efficient
this = positive climate feedback
For long-lived greenhouse gases, the current radiative forcing comes from …..
emissions over the past century
For shorter-lived gases, the current radiative forcing comes from ….
more recent emissions.
a pulse of methane (perturbation lifetime of…..
12.4 years
The UNFCCC Kyoto Protocol (1997) and Paris Agreement (2015) are multi-gas agreements which put limits on emissions of a groups of gases (Kyoto) or require parties to ….
declare their intentions to limit emissions of a group of gases (Paris)
Multi-gas agreements require an…
exchange rate” to compare, e.g., a 1 kg emission of CH4 with a 1 kg emission of CO2
what is the most commonly used metric called? - comparing c02 and non c02 emissions
100-YEAR GLOBAL WARMING POTENTIAL (GWP (100)
whose choice was the metric of GWP 100 ?
GWP(100) is a UNFCCC choice not an IPCC one
The so-called “basket of gases” covered by multi-gas agreements generally include:
CO2, CH4, nitrous oxide, hydrofluorocarbons and a few other minor gases
They do not include emissions of ozone depleting gases; these are controlled under the Montreal Protocol that protects the ozone layer
what is a alternative metric to GWP and what does it offer in comparison?
Alternative metrics, like the Global Temperature Potential (GTP), offer a more accurate representation of the temperature impact of methane over shorter timeframes. Policymakers originally chose the 100-year timeframe somewhat arbitrarily, based on limited information available at the time. While GWP(100) isn’t perfect, it’s still commonly used, even as methane emissions continue to rise. However, it can be misleading when emissions remain constant or decline. Additionally, there are uncertainties surrounding the input parameters used to calculate GWP values, highlighting the complexity of accurately assessing the climate impact of different greenhouse gases.
methane GWP100 varies in numbers from….
21 to 30
how much is the estimated uncertainties in GWP values? percentage
30 percent depending on what gas
for developed countries what gas dominates at what percentage?
for agriculture dominated countries what gas dominates?
For many developed countries, CO2 dominates; ≈20% from non-CO2
For agriculture dominated countries (e.g., Brazil and New Zealand) non-CO2 emissions dominate, and more one-third is from methane. Hence their CO2 equivalent emissions are highly dependent on metric choice
what do ipcc reports say as time goes on?
blame humans more and more
