Introduction to Climate Systems (Week 2) - Post 1

(Introduction To Climate Systems-Week 2 Notes)
2.1-2.5

2.1 Notes

*By the end of this section, you will be able to:

1. Articulate the difference between weather and climate.
2. Describe the primary components of the Earth system: the atmosphere, hydrosphere, biosphere, and geosphere.
3. Explain how three primary factors each influence energy flow in Earth’s climate system: solar energy, reflectivity, and the greenhouse effect.

*We have energy coming in from the Sun, reflection of solar energy by various materials, and we have the greenhouse effect altering energy flows. Our four “materials” categories are intimately intertwined with the three “energy flow” categories. Considering materials together with energy flows yields places to look for mitigation options.

Weather and Climate Change

https://www.rmets.org/weather-and-climate

Weather

Weather is the state of the atmosphere at any given time…A meteorologist will describe the weather in terms of accurate measurements of temperature, humidity, rainfall, pressure and many other factors.

Space Weather

Around this time of year there is an increase in the number of occurrences of Aurora Borealis, or the Northern Lights. These are manifestations of extreme conditions and are caused by solar energy. Solar energy enters the earth's magnetic atmosphere and causes disruption of the earth's magnetic field.

Volcanoes affect weather

Volcanoes erupt and dump millions of tons of volcanic matter in to the air. The matter blocks out the sunlight, and in extreme cases will cause entire seasons of time to be colder then usual. Laki (1783), Tambora (1815), and Krakatau (1883) are all volcanic eruptions that caused extreme changes in weather for those who lived near them.

Hurricanes

Meteorological Organization (WMO) has used a pre-determined list of names for each ocean basin of the world, that for obvious reasons does not use the letters Q, U, X, Y or Z. When a storm like Hurricane Katrina strikes, that causes loss of life and/or widespread damage, the country most affected by the storm may ask the WMO to ‘retire’ the name from the list as an act of respect – some fifty names have been retired since 1978 in the Atlantic basin alone.

In fact, attributing the increase of events like Hurricanes to human-induced climate change is almost impossible with current climate models.  The current global models are too course a resolution to resolve features like Hurricanes.  Some studies have looked at embedding higher resolution regional climate models within the global predictions but can only give broad indications of trends that have a large degree of uncertainty.  What the climate models can do is to look at larger scale tropical storm systems as a surrogate for Hurricane development, but as yet these studies are inconclusive and an active area of research.

Weather Forecasting

Scientists’ have desired to predict weather as early as the bible times. The following are the three approaches that have been used to predict weather.

Point forecasting: Analysis of historical time series establishes a correlation between a present observation and a future occurrence.

Pattern forecasting: From the time that observations could be exchanged in real-time following the invention of the electric telegraph in 1840, weather forecasting agencies were created to collect observations and create maps of them for specific times.

Numerical weather prediction: The 19th century saw huge advances in understanding the behavior of the atmosphere as a gaseous fluid behaving according to the principles of Newtonian physics.

Climate

Climate describes what the average of weather will be over a period of time. It will include not just the mean, but the variability and extremes, as these can have big impacts.  Climate is usually defined for different seasons or months and averaged over a period of 30 years. So, we might read for a particular place that “The average maximum temperature in July is 25°C, with typically 2 days hotter than 30°C”, or “The average rainfall for June is a total of 35mm, with 10 days of no rain and 3 days where rainfall is more than 5mm”.

Aerosols and Climate

Once in the atmosphere, aerosols can have a variety of impacts. Aerosols reflect and absorb radiation from the sun. Thus, a large concentration of most aerosol types will tend to scatter sunlight back to space, preventing the direct beam reaching the Earth's surface. This can lead to a cooling of the earth's surface…Whilst the direct beam is prevented from reaching the surface, more scattered light is available, and this affects photosynthesis. High aerosol concentrations can improve plant productivity, until other effects such as temperature or plant physiological issues become dominant…Aerosols are also responsible for clouds, and rainfall. Cloud droplets require an initial "seed" to start the condensation of water - this is provided by aerosols. Changes in aerosol can therefore lead to changes in cloud properties.

Aerosols have also been proposed as a means of mitigating greenhouse gas warming (geo-engineering), either by using them near the Earth's surface to make extra clouds, or by injecting them into the stratosphere to reflect the sun's radiation to space.  However, the impacts of such scheme are complex and uncertain.

Energy and Climate

Radiation comes in from the sun (solar radiation at short wavelengths), and everybody radiates according to its temperature (proportional to the fourth power of absolute temperature), so that on Earth we, and the surface and atmosphere radiate at infrared wavelengths. -Weather and climate on Earth are determined by the amount and distribution of incoming radiation from the sun. For an equilibrium climate, global mean outgoing longwave radiation (OLR) necessarily balances the incoming absorbed solar radiation (ASR), but with redistributions of energy within the climate system to enable this to happen on a global basis.

The human influence on climate, arising mostly from the changing composition of the atmosphere, affects energy flows. Increasing concentrations of carbon dioxide and other greenhouse gases have led to a post-2000 imbalance at the TOA of 0.9±0.5 W m-2 (Trenberth et al. 2009) (Fig. 1), that produces “global warming”, or more correctly, an energy imbalance.  Tracking how much extra energy has gone back to space and where this energy has accumulated is possible, with reasonable closure for 1993 to 2003.

Climate Change by Tim Palmer

From such a disinterested scientific perspective, the threat of substantial, even calamitous, climate change is unequivocal. However, at the same time, I myself do not believe we are yet doing all that is scientifically and technically possible to really understand and quantify the nature of this threat. There is no more challenging problem in computational science than that of simulating and predicting climate. With our current relatively low-resolution global climate models, we are looking at our future climate through frosted and somewhat distorted glass. This is particularly so when we try to simulate and understand regional climate…so the nations of the world should come together to fund the sort of supercomputers that would allow us to simulate the climate of the coming century with much greater reliability than is currently possible.  The impact that this will have for mitigation, adaptation and geoengineering policies is likely to be enormous.

http://www.eo.ucar.edu/basics/

Weather: is the mix of events that happen each day in our atmosphere including temperature, rainfall and humidity. Weather is not the same everywhere. Perhaps it is hot, dry and sunny today where you live, but in other parts of the world it is cloudy, raining or even snowing.

Climate: in your place on the globe controls the weather where you live. Climate is the average weather pattern in a place over many years. So, the climate of Antarctica is quite different than the climate of a tropical island.

Climates are changing: because our Earth is warming, according to the research of scientists. Does this contribute to a warm summer day? It may, however global climate change is actually much more complicated than that.

Climate Change Effects

According to the IPCC’s current findings, the world’s surface air temperature has increased an average of 0.6°C (1.0 °F) during the 20th Century. That may not sound like very much, but even one degree can cause changes around the world.

Sea-Level Rise

Sea level has risen 10-20 cm (4-8 inches) during the 20th century…Models predict that sea level may rise as much as 85 cm (33 inches) during the 21st century. This would have dramatic effects on low-lying coastal communities as shoreline erosion threatens houses and freshwater supplies are contaminated with salty water. Certain natural ecosystems such as wetlands and coral reefs would also be in jeopardy as sea level rises so rapidly.

 Melting of Arctic Sea Ice

Melting Arctic sea ice may eventually lead to global changes in water circulation. The water from melted ice forms a layer at the sea surface that is less dense than the underlying water because it is less salty, potentially preventing the pattern of deep ocean currents from rising to the surface. Additionally, melting sea ice speeds up warming of the Arctic because water absorbs 80% of sunlight, about the same amount that the cover of sea ice used to reflect.

Warmer Oceans

Warmed sea-surface temperatures have been responsible for major destruction and will continue to wreak havoc as global temperatures climb. About a quarter of the world’s coral reefs have died in the last few decades, many of them affected by coral bleaching, a process tied directly to warming waters which weakens the coral animals. Future warming may have consequences for other communities of marine life as well.

Floods

Warmer temperatures cause more evaporation of water, which, as part of the water cycle, eventually leads to more precipitation. In fact, the world has seen a 5-10% increase in precipitation over the past century. However, the frequency of heavy rainfall events generally is likely to rise with global warming, increasing the potential for flooding.

Droughts

While some parts of the world are treated to more precipitation as global warming persists, other parts may experience increased levels of drought as temperatures rise. This is because places that are typically dry, such as the centers of continents, will experience even more evaporation as global temperatures climb.

Heat Waves

Heat waves are a great health risk. For example, a 1995 heat wave in Chicago caused 514 heat-related deaths. As global temperatures warm, there is likely to be an increase in the number of heat waves and their intensity, leading to an increase in the number of heat related deaths.

Warmer Winters

There is already evidence in Europe that the growing season has extended several days since the 1960s, with spring plants now blooming about 6 days earlier and fall colors coming about 5 days later.

Ecosystems Change

Scientists believe that ecosystems will respond to climate change by migrating to new locations that are more like the current climate, or they will change, adapting to the new climate, causing some species to become less abundant or locally extinct.

Agriculture

With drought affecting some areas and intensifying in the tropics, many areas are becoming unsustainable for agriculture. In areas that are already dry and hot the amount of food harvests will likely decrease. Scientists predict that by the 2080s, about 80 million people, mostly within Africa, will be hungry because of climate change.

General Notes

Many people argue that present day climate change is a natural process that has been happening since the beginning of time. If climate has always changed, then what is global warming so controversial today? While climate change has always occurred, by mining and burning fossil fuels many scientists believe that we are greatly accelerating the warming process, so that we may have unwittingly opened a Pandora’s box of unexpected, uncontrollable changes to life on our planet. The rate of change today is rapidly increasing to the point that scientists are concerned that life on Earth, including humans, will not have time to adapt to the changing conditions.

Video Notes

Crucial Components of the Climate System:

*Rocks

Atmosphere

*(Greenhouse) gasses

Aerosols

*Water

*Life

*All of the four big players that's rocks, water, gases, and life participate somehow in moderating the energy flows within earth's climate system.

Key points:

+ The atmosphere, hydrosphere, biosphere, and geosphere comprise a useful way to describe the basic reservoirs for materials on earth.

+ Materials constantly exchange among these reservoirs.

+ The primary source of energy for Earth’s climate system is the Sun.

+ The reflection characteristics of Earth materials in all four reservoirs influence how much solar energy reflects directly back to outer space.

+ Greenhouse gases in the atmosphere, with concentrations controlled by flows of material to and from the atmosphere and the other three reservoirs, act to slow the passage of energy from Earth’s surface back to space, warming Earth’s surface and lower atmosphere. 

2.2 Notes

Learning Goals-

By the end of this section, you will be able to:

+Translate among Kelvin, Celsius, and Fahrenheit temperature scales.

+Generate everyday analogies to describe energy (in Joules) and energy fluxes (in Watts/meter²) in intuitive terms.

+Given a change in energy flux, estimate a global temperature change using Earth’s climate sensitivity.

Converting between Fahrenheit, Kelvin, and Celsius-

(In this course, we'll primarily use Celsius and kelvin since those are the scales used in climate science)

0 C = 32 F

From there, for every 10 degrees Celsius you go up, you add 18 degrees Fahrenheit. 

Furthermore, for every 1 degree Celsius its about 2 degrees Fahrenheit.

C = (F-30)/2

K = ° C + 273

My Practice Conversions-

(Celsius to Fahrenheit)

18 C - 0 F / 25 C – 60 F / 3 C – 6 F / 33 C – 74 F

(Fahrenheit to Celsius)

78 F – 34 C / 41 F – 5.5 C / 66 F – 18 C / 80 F – 25 C

(Celsius to Kelvin)

22 C – 295 K / 10 C – 283 K

(Kelvin to Celsius)

304 K – 31 C / 278 K – 5 C

-Joules are the units that we use in climate science.

4.2 Kilojoules is equal to 1 Kilocalorie (Food Calorie)

1 Kilojoule is equal to 1,000 Joules

*So 1 food calorie is equal to about 4,200 Joules of energy

 Joules per second = Watts

Climate Sensitivity

How much warming do you get for a given increase in energy?

For every 1 Watt/meter^2 (watt- Joules (energy) per second) increase earth’s surface temperature goes up by 3/4^th of a degree.

Example: If 4 W/m^2 of energy is added to earth, earth’s surface temperature will increase by about 3 degrees.

So what could increase earth’s energy by 4 W/m^2?

A handy and fairly common way to think about the climate sensitivity and relate it to a change in the greenhouse effect is that if the concentration of carbon dioxide in the atmosphere were to double, we'd get about an additional four watts per meter squared on average, over each square meter of earth's surface. This number includes some of the fast responses in the climate system that occur when CO2 increases, like increasing water vapor in the atmosphere. The effect, therefore, of doubling CO2 concentration is a temperature increase of about three degrees Celsius after the earth equilibrates to its new energy balance. We could get that four watts per meter squared by doubling from 100 parts per million to 200 parts per million CO2, and then we could get an additional four watts per meter squared by doubling from 200 parts per million to 400 parts per million. Or the four watts per meter squared might come from some other aspect of the climate system, perhaps an ice sheet expands, so that four more watts per meter squared gets reflected back to space, and earth cools by 3 degrees. Perhaps soot landing on white ice decreases the ice's reflectivity and adds more watts per meter squared absorbed by earth's surface. Or perhaps reflective aerosols increase or decrease. The combination of changes in the climate system, many of them interconnected, determine changes in the energy balance over time and therefore changes in temperature over time.

Ultimately, the amount of energy in earth's climate system sets the planet's temperature. Temperature is one of the key metrics when we talk about climate. A little bit more energy can change our planet's temperature. Even though a degree or two might not seem like very much, it can make a big difference.

2.3 Notes

Learning Goals

By the end of this section, you will be able to:

+Define stock, flow, and feedback.

+Explain how the combined history of inflows and outflows determines a stock.

+Predict what happens to stocks and flows of energy and materials when a system is perturbed.

+Construct examples of both amplifying and stabilizing feedbacks.

Video Notes

It's the historical combination of stock and flow that determines the state of the system at any particular time.

Stock- The amount of something somewhere at sometime

Flow- A rate at which stuff adds or subtracts from a stock (since flow is a rate, there’s always an element of time included)

-There are 2 types of flow, inflow and outflow

If you’ve ever been in the position where you’ve had to bail out a leaking boat, you have some experience with the balance of inflow and outflow.

To summarize stock and flow, the stock at any moment, is the result of the combined history of inflow and outflow. At equilibrium, or steady state, inflow equals outflow. We can have equilibrium at a wide range of different levels. However, if inflow is not equal to outflow, the stock will change.

Feedback- The amount of stock influences a flow in or out of that stock, and the flow in turn, feeds back to influence the stock. Feedback happens when some perturbation occurs, and the system responds, either by amplifying the perturbation, or stabilizing it.

Stabilizing/ Balancing Feedback- A feedback that brings the system back toward equilibrium.

Amplifying Feedback- A response to a perturbation that pushes the system in the same direction as the initial perturbation pushed it.

*Climate Connection- If something caused global temp. to increase, an amplifying feedback would increase global temp. further, which would keep the feedback process going. The same can happen in reversal as well.

Summary

In summary, earth’s climate system has lots of different stocks, lots of different flows among these stocks, and many feedback processes. Some feedbacks in the climate system amplify perturbations, and some feedbacks stabilize the system after a perturbation.

Stock and Flow Activity

      Write down two stocks involved in Earth’s climate system

a)    The amount of water covering the Earth

b)    The amount of forest covering the Earth

          Write down the inflows and outflows to and from these stocks

a)    Inflow- the amount of precipitation, outflow- the amount of evaporation

b)    Inflow- new trees growing due to natural, and man made processes, Outflow- trees dying due to natural processes, and being cut down through deforestation by man.

      Write down whether you think the flows are in balance or out of balance.

a)    There is a set amount of water on earth, however due to warming of the climate ice caps are melting and creating the inflow of water to be more than the outflow of, causing more water to cover Earth’s surface. 

b)    Due to rapid deforestation by the human populations on Earth, the stock of forest covering Earth’s surface is decreasing. The inflow of planting new trees and natural processes is less then the outflow of trees being cut down

2.4 Notes

Learning Goals

By the end of this section, you will be able to:

+Describe Earth’s geologic variability over the past million years.

+Explain evidence that supports the orbital theory of naturally recurring ice ages.

+Formulate a hypothesis describing the best orbital configuration to grow (or melt) a continental ice sheet.

+Construct feedback loops that likely amplified climate cycles over the past million years.

Milankovitch Cycles

Eccentricity- The shape of Earth’s orbit

Obliquity- The tilt of its axis

Precession- The direction of its axis

Milankovitch used these cycles to explain the advance and retreat of the polar ice caps. These cycles play a role in Earth’s climate.

-Eccentricity-

A measure of how elliptical Earth’s orbit is. A planet’s closest approach to the sun is called the perihelion, and the furthest distance is the aphelion. The eccentricity is a measure of how different these are.

The eccentricity of Earth’s orbit follows a long 100,000-year cycle. The eccentricity varies from a minimum of e=0.0005 to a maximum of e=0.0607. The larger the eccentricity, the greater the difference in solar radiation that reaches the Earth at perihelion versus aphelion.

-Obliquity-

Refers to the tilt of the Earth’s axis relative to the plane of its orbit. The Earth’s tilt now equals 23.5 degrees. If the obliquity were 0 degrees, there would be no seasons.

The obliquity of the Earth’s orbit follows a 40,00-year cycle. The obliquity varies from a minimum of 22.1 degrees to a maximum 24.5 degrees. The larger the obliquity, the greater the difference in seasonal temperature.

-Precession-

Precession changes the direction of tilt of the Earth’s axis relative to its aphelion and perihelion.

The Earth wobbles like a spinning top which is running down. This wobble follows a 26,000-year cycle. The Earth’s axis now points at Polaris, our North Star. In 13,000 years it will point towards the star Vega. Precession is caused by the gravitational effects of the Sun and Moon. Currently, the Northern Hemisphere experiences winter when the Earth is closest to the sun. 13,000 years ago, winter occurred in the Northern Hemisphere when it was furthest from the sun.

The Milankovitch cycles result in long term fluctuations in the energy that reaches the Earth.

*Note- The seasons have everything to do with the tilt of Earth’s axis, not Earth’s distance from the sun.

Video Notes:

+Changes in Earth’s orbit alter the amount and distribution of incoming solar radiation 

Earth receives.

+Low seasonal contrast helps grow ice sheets; high seasonal contrast helps melt ice sheets. (Obliquity)

+The total incoming energy doesn’t vary enough to account for the large observed change in climate, but feedbacks, like the ice-albedo (ice sheets) feedback and the CO2-temperature feedback amplify small perturbations and help produce larger changes in Earth’s climate.

+The past million years is our geologic backdrop against which we can compare today’s rates of change in climate and absolute values of climate parameters. Today’s rates of change, and values like atmospheric CO2 are higher than observed in the past million years. 

2.5 Notes

 Learning Goals

By the end of this section, you will be able to:

+Describe trajectories of various climate metrics since the Industrial Revolution (e.g. temperature, sea level, ice cover, greenhouse gas concentrations).

+Compare today’s climate trajectories and rates of change to the climate context of the past one million years.

Video Notes

Inflow of heat is currently less then the outflow of heat. So where is all the heat going? Because it takes a large amount of energy to heat the ocean, and because the ocean takes up so much space on earth, the ocean is absorbing increasingly larger proportions of the inflow of heat.

When water heats up it expands in volume. So imagine the entire ocean heats up and thus the entire ocean expands in volume. Since the bottom of the ocean isn’t changing very fast, the only place for that extra volume to go is upward, raising the water level. This expansion of ocean water is responsible for about half the global sea level rise. Melting ice on land accounts for the other half.

Video 2 Notes

+Measurements of climate-related parameters indicate that recent global climate trends are toward:

Higher temperatures

Higher sea levels

Lower summer sea ice extent

Melting of land ice from ice sheets on Antarctica and Greenland

Higher concentrations of greenhouse gases

+For some of these, like greenhouse gas concentrations, the values today exceed values observed over many tens of thousands of years.

+Rates of change in some of these parameters are rapid today compared to the pre-industrial past.