homework

GEO 344 Weather and Climate Prof. Stuart Evans

Lecture 25 Climate Forecasting

Not raining

All these photos come from the clouds lecture

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How to extend the life of a thunderstorm

Ordinary thunderstorms create their own death: their updrafts and rainfall lead to downdrafts that cut off their energy source.

How can this be prevented?

Severe Thunderstorms • How to separate up and down

drafts? Tilt the thunderstorm with wind shear.

• Major difference from air mass thunderstorms: • They are long-lived (1-3 hours) • UPDRAFTS are separated from DOWNDRAFTS

• NWS criteria (any of below qualifies as severe) • 1” Hail • 50 kt surface wind gust • Tornado

Stronger wind aloft (“wind shear”) tilts the storm

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1) Colliding ice particles exchange electrons. Big falling ice steals the electrons. The bottom of the cloud becomes positively charged. Top positively charged

Lightning creation

Hazards: Hail

Hailstones carried in updrafts, start falling, get caught again, carried upwards, fall again, sometimes many cycles before falling out.

The more cycles of growth, the bigger the hailstone (really strong updrafts are required to catch a big hailstone)

Surrounded by mountains

No topography Surrounded by mountains

Surrounded by mountains

Warsaw More/dirtier industry Dirtier power generation Greater population / more cars More stable weather

Geneva Stronger pollution regulations More rain

Dec. 7, 2013

Dec. 8, 2013

Dec. 9, 2013

Thick smog Can’t see the ground Stable atmosphere

Lots of clouds Storm with wind and rain Unstable atmosphere

Much clearer Can see the ground

Gray = smoke-fog

Forecasting All three forecast providers initially warmed their prediction, then cooled it as the day approached. Actual high: 50 °F

At first a decreasing likelihood of rain, then an increase again. Actual: no rain

Likely reasons for changes: new data / changing conditions Likely reasons for disagreement: differing expert opinion, different data sources, different weather models

Hurricane Damage

• Damage in hurricanes are caused by: • Storm surge

• High winds pushing water towards the land • Inland Flooding from rain • Winds

• Financial damage from hurricanes is increasing, but this is primarily due to more people living on the coast

Wind is stronger to hurricane’s right side Example: hurricane is moving at 50 kph, has rotating winds of 175 kph

Winds add together on right side

Winds subtract from each other on left side

Winds push water towards land with no place else to goWinds pull water away from land

Worst storm surge to the right of the hurricane

Storm surge: high winds pushing water towards land

Storm tide = normal tide + storm surge If the storm hits at high tide, then the two add together, making damage worse If the storm hits at low tide, then the two subtract, making damage less

Battering waves on top of storm tide

Requirements for Hurricanes

• Warm ocean temperatures: first requirement for hurricanes • Hurricanes weaken when they pass over land due to lack of

evaporation • Sea surface temperatures must be above 26o C (79o F)

Last time:

Energy balance tells us if the Earth will warm or cool

We can change energy balance through the greenhouse effect

The strength of the greenhouse effect depends on the concentration of greenhouse gases

How do we forecast this for the future?

The greenhouse effect

Energy gets in through glass

Energy can’t get out through glass

Energy gets in through atmosphere

Energy has hard time getting out through atmosphere

More GHGs = thicker / more layers of atmosphere harder for infrared to escape surface gets hotter

equivalent to more or thicker blankets

Greenhouse gases strengthen the greenhouse effect

Venus 98% carbon dioxide 735 K

Earth 0.04% carbon dioxide 289K

Names of scenariosEmissions scenarios

Year

“Business-as-usual” How much CO2 gets emitted by society is not answered by physics.

Instead, economics, demographics, and technology determine how much carbon dioxide will be emitted.

Those things are uncertain for the future, so we use a range of emissions scenarios to cover the spread of how much we might emit in the future.

Dessler Figure 8.5

RC P8

.5

RCP6

RCP4.5

RCP2.6

Maybe we want to be on this temperature track and not this one

A lot of people wanted to know about global warming solutions

Emission scenarios

We create a range of possible greenhouse gas concentrations, called emission scenarios.

By making guesses at world population, wealth, and technology, we can guess at future greenhouse gas concentrations.

I = P * A * T

Emissions (CO2) (the I is for impacts) Population

Affluence (wealth)

Greenhouse gas intensity (the T is for technology)

Kaya identity can be adapted for other emissions

I = P * A * T

CO2 emissions= People * GDP * CO2 people GDP

carbon emissions = how many people you have * how wealthy people are * how much carbon is creating while creating wealth

Gross Domestic Product (the size of a country’s economy)

Greenhouse gas intensity

I = P * A * T

T is how much carbon gets emitted in the process of running the economy: CO2 GDP

Can be broken down into two parts: how much energy it take to make money, “energy intensity” how much carbon is emitted to make energy, “carbon intensity”

T = EI * CI

Energy intensity Carbon intensity

Greenhouse gas intensity

T = EI * CI

Greenhouse gas intensity = Energy * Carbon = Carbon GDP Energy GDP

Energy intensity: how inefficiently we use energy (larger = less efficient)

Carbon intensity: how inefficiently we create energy (larger = less efficient)

IPAT terms through time

Population and affluence have both increased

Efficiency of energy use and creation have improved, but not as fast

I = P * A * T (# of people)

I = P * A * T ($ / person)

I = P * A * T (CO2 / $)

Darker blue: Greater GHG intensity (more CO2 / $)

Lighter blue: Lower GHG intensity (less CO2 / $)

It can be a little tricky to decide what counts as carbon emissions. Just what comes out of tailpipes / smokestacks? Or…

Big emissions divided by big economy = medium GHG intensity

Basically no emissions divided by small economy = small GHG intensity

I = P * A * T (CO2 / $)

e.g. deforestation

Including deforestation as “emissions” makes the tropics appear a much bigger source

Energy intensity (energy used / $)

Dark blue– low energy intensity

Light blue – high energy intensity

Technology grams of CO2 per

kilowatt-hour Coal 820 Gas 490

Biomass 230 Solar photovoltaic 48

Geothermal 38 Concentrated solar

power 27

Hydropower 24 Wind Offshore 12

Nuclear 12 Wind Onshore 11

Carbon intensity (CO2 / energy generated)

Extremely variable, but the general order/magnitude is about right

Carbon intensity (CO2 / energy generated)

Green: Low carbon intensity

Red: High carbon intensity

I = P * A * T (CO2)

I = P * A * T (CO2)

= X

X

populationemissions

affluence

GHG intensity

Making an emission scenario for the future

1. Predict how these four terms will change in the future

2. Multiply them together

I = P * A * T

Future emissions

Global climate projections

What society chooses Physics and Chemistry

RC P8

.5

RCP6

RCP4.5

RCP2.6

Uncertainty in the details

of how the climate system

responds to emissions

Uncertainty in future human behavior (how much greenhouse gas will be emitted)

Global average temperature anomaly (compared to today) in future times

Dessler Figure 9.1 Years 2046-2065 (Our lifetimes)

Years 2081-2100 (Next generation)

Years 2181-2200 (Future generations)

How will temperatures change if we reduce CO2 emissions today?

RCP2.6

… if we reduce CO2 emissions later (2040)? RCP

4.5

… if we do not reduce CO2 emissions but our children do (2080)?

RCP 6

… if we do not reduce CO2 emissions? (“business as usual”)

RCP 8.5 Temperature change (anomaly), compared to 1986-2005 reference period

Dessler Figure 9.1 Years 2046-2065 (Our lifetimes)

Years 2081-2100 (Next generation)

Years 2181-2200 (Future generations)

How will temperatures change if we reduce CO2 emissions today?

RCP2.6

… if we reduce CO2 emissions later (2040)? RCP4.5

… if we do not reduce CO2 emissions but our children do (2080)?

RCP 6

… if we do not reduce CO2 emissions? (“business as usual”)

RCP 8.5

Dessler Figure 9.1 Years 2046-2065 (Our lifetimes)

Years 2081-2100 (Next generation)

Years 2181-2200 (Future generations)

How will temperatures change if we reduce CO2 emissions today?

RCP2.6

… if we reduce CO2 emissions later (2040)? RCP4.5

… if we do not reduce CO2 emissions but our children do (2060)?

RCP6

… if we do not reduce CO2 emissions? (“business as usual”)

RCP 8.5

Dessler Figure 9.1 Years 2046-2065 (Our lifetimes)

Years 2081-2100 (Next generation)

Years 2181-2200 (Future generations)

How will temperatures change if we reduce CO2 emissions today?

RCP2.6

… if we reduce CO2 emissions later (2040)? RCP4.5

… if we do not reduce CO2 emissions but our children do (2060)?

RCP6

… if we do not reduce CO2 emissions? (“business as usual”)

RCP8.5

Temperature difference compared to today

How will global temperatures change if we do not reduce CO2 emissions? (RCP8.5)

Are we doomed? Can we stop it?

Years 2046-2065 (Our lifetimes)

Years 2081-2100 (Next generation)

Years 2181-2200 (Future generations)

This row is how much is unavoidable RCP2.6

RCP4.5

RCP6

We can choose to avoid this row (is a choice, won’t happen by accident)

RCP8.5

Ho w h

ard do

we try

?

That’s all folks!

This was a rough second half of the semester and not at all how I would have liked to teach the class.

Course evaluations are still open through the weekend: these will be very valuable in designing courses for the future

To those who have stayed engaged here to the end: Thank You!

If you’ve made it here to the end of the semester, congratulations!