Introduction to Climate Modeling
(for non-science people)

Climate Modeling

Do We Need Models? (yes)

Humanity has always built models to better understand complicated observations -AND- serve as teaching tools. Building a working model proves "you are in possession of all the facts". Deviation from observation proves that your model works at some gross level but is missing some finer details.

Early Mechanical Models of the Solar System

In ancient times people built mechanical models of our solar system to predict the current location of the planets and stars. These models were based upon naked-eye observations and worked well until better observations indicated improvements were required. Model builders responded by adding epicycles to the planetary positions (perhaps this was just the easiest fix for a mechanical model).

In medieval times Nicolaus Copernicus suggested that a heliocentric system would simplify the models but this idea seemed too revolutionary to most people. Improved observations by Tycho Brahe coupled with mathematical analysis by Johannes Kepler proved that planetary orbits needed to be changed from circular to elliptical (how would the mechanical model builders accomplish this?). Telescopic observations by Galileo proved the heliocentric system was correct but now the Roman Catholic Church stood in the way of scientific progress. Perhaps scientists were avoiding being burned at the stake when they stated "we don't really believe in the heliocentric system, it just simplifies our models".

Improving the Solar System Model

Most basic principles of nature can be described using simple mathematics. For example, Newton's Three Laws of Motion and Newton's Law of Universal Gravitation can each be expressed using simple algebraic equations. However, combining them with Kepler's Laws of Planetary Motion into a complicated mathematical model representing planetary motion is much more difficult.

Although work done by people such as Urbain Le Verrier (who used pen and paper to predict the location of an unknown planet eventually named Uranus) is unbelievably impressive, a computer is required to model known planetary and stellar motion. A mechanical model is no longer possible or practical.

If you don't believe me then consider this: if the Earth was the only planet orbiting the Sun, the shape of Earth's orbit would eventually degrade into a circle. However, the gravitational tugs of other planets causes the shape of Earth's orbit to change from circular to elliptical and back in a time period of 400,000 years. This theory was also worked out using only pen-and-paper by the Serbian mathematician Milutin Milankovitch but remained a mathematical abstraction until computer modeling was applied. BTW, other aspects of Milankovitch Cycles combine in such a way to enable glaciations (ice ages) every 100,000 years or so. Our current interglacial period (known as the Holocene) started 11,700 years ago.

Computer Limitations (and Science Limitations)

Because computers can be used to calculate equations many millions of times faster than any human, modern life would be impossible without them. For example, who could imagine any government manually processing our income tax claims? However, computers do have limitations most people are not aware of.

Experiment: the next time you pour cream into your coffee, carefully watch the swirling clouds as the two fluids (liquids in this case) mix. This turbulent behavior is partly based upon a combination of chaos theory and fluid dynamics. Unfortunately no computer on the planet now (2010), or any time soon, is able to accurately model this. Think about it: you are only mixing two liquids so why is the resulting action so complicated? To make matters worse, every time you perform the coffee-cream experiment you will observe a slightly different result. So maybe we need to consider more details like: exact volumes and temperatures of each liquid, height the cream is poured from, place where it has been poured into, exact components of the cream, exact components of the coffee, viscosities of both liquids, smoothness and shape of the container, swirling speed of the coffee from the initial filling event, etc.

It turns out that an accurate computer model will require us to mathematically compute the properties and trajectory of every molecule. Since humanity won't be doing this anytime soon, perhaps we can cut corners by only computing the average action of each deciliter (one tenth of a liter) at one minute intervals. As long as the simulation gives us a homogenous mixture after 2 minutes and possibly allows the cream to settle to the bottom after a couple of hours then our computer simulation might be good enough.

Future improvements in computer technology along with advances in computer programming techniques might allow us to slowly reduce the average volume modeled along with the average time-period being simulated. And yet we are still only talking about a cup of coffee.

Modeling Earth's Climate

Simulating Earth's Weather with Pencil and Paper

The first attempt to do a model Earth's weather was done with pencil and paper using something called the two-box model. This scheme (which is still used today to teach science students) uses two boxes to model the whole earth. The top box represents Earth's atmosphere while the bottom box represents Earth's surface. It is obviously very simplistic but a little tinkering provides a good starting point to other more complicated models.

The two-box model was replaced with two-dimensional models, three-dimensional models, then finally cell models. A complete description of these models is beyond the scope of this introduction but you can Google the phrases to investigate further.

I recently stumbled upon a first serious attempt to do a cell model which was attempted in 1922 obviously without the aid of a computer. Excerpt from: http://www.aip.org/history/climate/GCM.htm

Weather vs. Climate

We all know that weather reports today are not very accurate, and yet, they have improved quite a bit since the 1950s. In certain instances, such as tropical depressions which can develop into hurricanes, weather reports may be reasonably accurate over a period of 7-10 days. But just like our cup-of-coffee example described above, skipping over the details will allow us to predict the long-term trends. This is the major difference Weather and Climate and I should point out that "climate models" are much better than "weather models".

Even if it was possible to accurately model climate or weather, you cannot mathematically model all the inputs. For example here are two (of many) events which appear to act randomly:

Volcanoes

There are 500 active volcanoes on Earth today with as many as 1,500 potentially active volcanoes. However, there does not appear to be any mathematical pattern which would describe their frequency or intensity. To make matters worse, all active volcanoes release a variable (random) volume of CO₂ which will increases the greenhouse effect while. Volcanoes also release larger volumes of light-colored particulate matter (which directly reflects sunlight back into space) as well as sulphur dioxide compounds (which stimulate cloud formation).

Added Complication: CO₂ can remain in the atmosphere for 100 years or more. The effects of white particulate matter and/or sulphur dioxide will only last one to two years. So what might initially appear to be a short-term cooling event (like Mount Pinatubo in 1991) eventually will be a long term warming event.

Humans

One cigarette improperly discarded in a National Park occasionally will start a massive forest fire resulting in a massive release of heat, smoke, and CO₂ into the atmosphere.

These seemingly random events (along with the previously mentioned turbulent behavior of fluids) need to be manually inserted into our climate models.

 Simulating Earth's Climate (a very simple starting model)

1. the quantity of solar energy entering each zone over the course of a day
2. the quantity of energy temporarily absorbed by: soil, melting ice, warming water, and evaporation
3. the quantity of energy is being radiated back into space
4. the quantity of energy temporarily released by: freezing water, and precipitation.

Because there is more sunlight at the equator, a greater amount of sunlight will be absorbed in rows A + B than rows N + S. In fact, you may wish to visualize an oval of light stretched from North to South and wide enough to cover two columns at the equator. Because the surface of the globe is spinning west-to-east (left to right), our view of the solar oval will be seen to move right-to-left.

Because the surface of the globe is spinning west-to-east while the atmosphere wants to stay put, an apparent east-to-west wind will be blowing over the equator so we'll need equations to describe that as well. Depending upon how you handle parameter communication between zone boundaries, you will probably need at least 28 (12v+16h) inter-zone calculations. (column 4 zones are connected to column 1 zones; there are no zones above row N or below row S)

This means that each simulated tick of the clock will require at least 44 (16 + 28) calculations. You might be able to try this with pen and paper but it will be time consuming and error prone. Moving the simulation into a computer will allow you to introduce larger (more accurate) equations into each location.

If you are brave then you'll need to introduce seasonal changes. This means that the rows N + A would receive peak daylight in June while rows B + S would receive peak daylight in December. It might be easier to visualize a single sine wave superimposed upon our model where the phase shifts over the course of a year.

Simulating Earth's Climate (more layers)

Although solar energy directly heats the ground wherever it falls on land, heated ocean water tends to redistribute energy via events as small as evaporation and as large as hurricanes, which all occur in the atmosphere. Ocean energy is also responsible for water currents as small as the Gulf Stream and as large as the Thermohaline Circulation which all occur at, or below, the surface. This means we might want to introduce a second layer so atmospheric events could be simulated in the upper layer while ocean events would be simulated in the lower layer.

After updating equations in the 32 zones to reflect land vs. water, we now need 16 additional equations to describe the flow of energy (zone by zone) between the layers. We now require 60 (44+16) calculations for each tick of the simulation clock. Yikes!

But do we have enough squares? More land exists in the Northern Hemisphere so more squares would allow us to code for that. Also, since uplift formed the Panamanian Land Bridge 3 million years ago, ocean currents have changed in such a way that glaciations are much more common. If we want to model ocean currents then we will need a lot more zones.

JASON - Climate Models commisiioned by the U.S. Government

• preindustrial CO₂ concentrations in the atmosphere expected to double by 2035 (today's models indicate 2050-2100 depending upon human actions)
• temperatures would rise by 2-3 C by the end of the 21st century (current models agree)
• temperatures at polar caps would rise much faster; perhaps by 10-12 C (current models agree)
• read more: The Long-term Impacts of Increasing Atmospheric Carbon Dioxide Levels
  
  (caveat: some temperatures in this report are given in degree changes Celsius while others are given in degree changes Kelvin. Multiply either of these numbers by 9/5 to get degree changes Fahrenheit.

Simulating Earth's Climate in Large Data Centers

This associated image and text in this section was borrowed from a NOAA (National Oceanic and Atmospheric Administration) web site. It appears to be using either 2.5 or 3 layers and thousands of zones.

Climate models are systems of differential equations based on the basic laws of physics, fluid motion, and chemistry. To "run" a model, scientists divide the planet into a 3-dimensional grid, apply the basic equations, and evaluate the results. Atmospheric models calculate winds, heat transfer, radiation, relative humidity, and surface hydrology within each grid and evaluate interactions with neighboring points.

• The First Climate Model (200^th anniversary of NOAA)
  1. Ocean and Atmosphere Interactions
  2. Testing the Notion of Global Warming
  3. The First Climate Model
  4. Modern Model Descendants
• Climate Modeling (introduction to climate modeling)
  • Video: Climate Modeling 101 - Grid Resolution (NOAA Grid Sizes over the years)

NASA Links:

• http://www.nasa.gov/topics/earth/features/perpetual-ocean.html 3-minute video
  • This is a data-derived animation of ocean surface currents from June 2005 to December 2007 from NASA satellites. Watch how bigger currents like the Gulf Stream in the Atlantic Ocean and the Kuroshio in the Pacific carry warm waters across thousands of miles at speeds greater than four miles per hour (six kilometers per hour); how coastal currents like the Agulhas in the Southern Hemisphere move equatorial waters toward Earth's poles; and how thousands of other ocean currents are confined to particular regions and form slow-moving, circular pools called eddies.
  • The visualization covers the period June 2005 to December 2007 and is based on a synthesis of a numerical model with observational data, created by a NASA project called Estimating the Circulation and Climate of the Ocean, or ECCO for short. ECCO is a joint project between the Massachusetts Institute of Technology and NASA's Jet Propulsion Laboratory in Pasadena, California. ECCO uses advanced mathematical tools to combine observations with the MIT numerical ocean model to obtain realistic descriptions of how ocean circulation evolves over time.

Departing Thoughts on Modeling

• Some claim that since weather can't be predicted then neither can climate
  • see weather vs. climate to see why this view is flawed
     
• Some claim that there are probably too many uncertainties to consider
  • this usually comes from people with no formal education in science
     
• Some claim that computer science is too primitive
  • this mostly comes from non-computer people; while computer people are cautious they also know about Moore's Law which states that computer power doubles every 18 months (computer power has increased by a factor of one hundred million between 1970 and 2011)
     
    
• Then there are a small number of political types who claim that climate scientists are part of some world-wide liberal conspiracy
  • after reading Merchants of Doubt I think many Americans have been swayed by a right-wing extreme-capitalist conspiracy.

The truth of the matter is that all the science denial is based on money. Everyone knows an obscene amount of money is based upon the sale of illicit drugs, like heroin and cocaine, but the money made from fossil fuels makes drug money look like chump-change by comparison. Big energy companies just don't want to kill the goose that lays the golden egg.

Facts based on modern (direct-measured) data:

• All 25 accepted climate models are able to accurately model Earth's past climate from 1860 forward (1860 provided humanity with accurate world-wide temperature measurements due to the manufacture and sale of inexpensive thermometers).
   
• Scientists do not pick one model while discarding others; they publish the results from all models then plot them all between confidence lines.
   
• In the case of unexpected natural events like the volcanic explosion of Mount Pinatubo, climate models must produce similar results when the unexpected natural event is inserted in the simulation.
   
• All models all agree that "earth's climate is getting warmer and it is mainly due to a combination of man-made (anthropogenic) warming AND natural warming (the previous glaciation only ended 11,700 years ago)". Not one climate model shows our environment getting cooler. The models do disagree with the point-of-no-return dates being anywhere from 2015 to 2050.
   
• There are more weather satellites in orbit now than at any previous time and their measurements are being used to fine-tune climate models. Some satellites continuously measure Earth's surface (land and water) temperature over every 16 km (10 mile) square. Others measure glacial flow.

  Caveat: Humans can not "directly" measure temperatures from space. Why? Temperature is inferred by:
  

  1. Measuring infrared radiation which is partially absorbed by ever-changing atmospheric gases between the heat-source and the measuring instrument.
      
  2. Measuring the microwave radiation emitted by atmospheric gases (works like a microwave oven in reverse)

  These readings are mathematically translated (the subject of some debate) into atmospheric temperatures. It is virtually impossible to use satellites to measure temperature (with certainty) from various atmospheric altitudes.

• The Arctic and Greenland are melting at an unprecedented rate. The resulting influx of fresh water could affect the ocean currents like the Gulf Stream and the Thermohaline Circulation which distribute equatorial heat to places like Northern Europe. This means the current effects of global warming will cool some locations which will convince many people that global warming is not real.
   
• Increased heat is causing increased evaporation which causes rain to fall sooner. Many locations are now getting too much rain while locations down-wind are getting little or none. Therefore, "Global warming brings shifting in weather patterns"

Facts based upon pre-modern proxy data 

• Models based upon data before 1860 can be useful but are less reliable. Why?
  • Temperature
    • First off, while temperature measurements before 1860 exist, they are usually spotty. For example, the first known temperature measuring device is the Thermoscope produced by Galileo around 1592, but their restricted temperature range restricted them to [mostly] indoor use.
    •  Development continues with various people creating a sealed tube then adding an external scale, but it was Christian Huygens in 1665 who first proposed the idea of a standard scale based upon the melting and freezing points of water
    • In 1724, Daniel Fahrenheit creates a thermometer scheme based upon a scale with freezing point of 32 F and a boiling point of 212 F
    • In 1742, Anders Celsius creates a thermometer scheme based upon a scale with freezing point of 0 C and a boiling point of 100 C
    • There are numerous accounts of people keeping local records in England and Ireland some which are described here. Many of these records are now held by Britain's Royal Society of London. One very notable record was created by Thomas Hughes for Stroud (Gloucestershire) between 1775 and 1795.
  • Tree Rings
    • since the majority of trees which contain grow rings are found at mid latitudes (trees don't grow at either pole; trees at the equator do not have annual growth rings) this proxy measurement is only of use in the northern hemisphere
  • Corals
    • since coral only grows in warm water, this proxy measurement is only of value in a thick band around the equator.
  • Pollen, Dust, and CO₂ in Ice Cores
    • While CO₂ in ice cores provide a fairly accurate measurement of atmospheric carbon dioxide at the time the ice was formed, trapped pollen and volcanic dust only indicate those particles were in the vicinity of the freezing water.

•  Sunlight seems to vary by no more than one half of one percent. On its own, changes in sunlight do not do much but can add to other anomalous effects. Sunlight is somehow involved in small changes in the jet stream (which can have large effects upon Northern Hemisphere weather)
• Global climate (and weather) are continually affected by both El Nino and La Nina. This should be of little surprise since almost 50% of the Earth (the Pacific side) is covered by water.
• Volcanoes affect global climate and weather more than anyone ever realized. On average, they tend to cool more than heat.
• Some heating effects in one area may temporarily cause cooling in other areas. Remembering that the British Isles are warmed by the Gulf Stream (London and Moscow are almost at the same latitude so London should be a lot colder than it is), then anything which affects the Gulfstream could have devastating effects on North-Western Europe

• Facts:
  • The Medieval Warm Period was 2-3 degrees warmer in the UK but only a degree warmer in both Labrador and Northern Europe (based upon various proxies including tree rings). Proxies indicated lower warming elsewhere.
  • This warming coincides with a period of very low volcanic dust (observed in ice cores) combined with slightly higher solar output (C¹⁴ Dating).
  • Since volcanoes stimulate cloud formation by releasing of sulphur dioxides, a reduction in volcanic activity will result in more solar energy reaching the Earth
• Conclusion 1:
  • More solar energy reaching the Earth drove the gulf stream a little harder which primarily warmed: Greenland, Iceland, The British Isles, and Norway.
• Fact:
  • This warming anomaly appears to have lasted at least 300 years (950-1250).
  • Three hundred years of heating resulted in an acceleration of ice melt (as compared to the rate since the end of the ice age 11,700 years ago)
  • Any fresh water, including water from ice melt, can poison the descending (northern) end of the gulf stream
• Conclusion 2:
  • Once the gulf stream was partially poisoned with fresh water, any decease in solar energy (increased volcanic activity producing more clouds, deceased solar output, etc.) would flip warming in the other direction. This happened and we now know as the Little Ice Age which is thought to have started between 1250 and 1275 and ended ~ 1700
    Notes:
    • Starting and ending dates vary greatly depending upon which data are referenced
      • Some documents based upon human historical records use a starting date of 1350
      • Data based upon ice pack and glacial ice use 1250
    • Although solar energy was slightly reduced during this time, the effect was tiny compared to the loss of cloud cover
  • Like the medieval warm period, places affected the most by warming were similarly affected by cooling
  • Energy absorbed by Earth but not transported north by the Gulf Stream goes elsewhere and this is noticed in proxy records from other locations

My Two Cents:

External Links

• http://en.wikipedia.org/wiki/Earth_Simulator
• http://celebrating200years.noaa.gov/breakthroughs/climate_model/welcome.html
• www.southwestclimatechange.org/climate/modeling
  • How Climate Models Work
  • Global Scale Modeling
  • Uncertainty in Global Models
  • Regional Modeling
  • Downscaling Techniques
• http://en.wikipedia.org/wiki/Computer_simulation
• http://en.wikipedia.org/wiki/Weather_forecasting
• http://en.wikipedia.org/wiki/Climate_model
• http://en.wikipedia.org/wiki/Global_climate_model
• http://science.howstuffworks.com/climate-info.htm
• www.howstuffworks.com/probing-the-history-of-climate-change-info.htm
• www.manicore.com/anglais/documentation_a/greenhouse/model.html
• www2.sunysuffolk.edu/mandias/global_warming/climate_models_accuracy.html
• http://www.skepticalscience.com/climate-models-intermediate.htm - How reliable are climate models?
• NSR's climate science page

Videos

"High Quality" Video Collections at YouTube

• http://www.youtube.com/user/NASAexplorer
• http://www.youtube.com/user/greenman3610
• http://www.youtube.com/user/potholer54

Selected "High Quality" Climate Science Videos

What are Humanity's Alternatives?

Emission Scenarios (Using Computers to Model Alternatives for Humanity)

The "A1" scenario is subdivided into 3 basic subcategories:

Talking Points:

• The first official chart published by the IPCC contained the typo "A1F1" where they meant to publish "A1FI". All subsequent publications contain this typo (I guess they just want to remain consistent)
• The USA and Canada are firmly in A1
• Despite what has been reported in the Western press, China is shifting from A1F1 toward A1B and may end up at A1T just by inertia. Once they begin running their factories with zero-cost energy (e.g. no fossil fuels) they will permanently dominate the world economy.
• There are too many humans on Earth to believe we would ever go extinct but I am convinced that current human culture will not survive unless humanity switches to scenarios A1T or B1
• Humanity is expected to hit 7 billion sometime in 2012 but there many scientists are now coming around to the idea that this number needs to drop back to 6 billion or perhaps even 5. It is one thing to have human beings living off the land in a pre-industrial fashion; it is quite something else to have 7 billion people living like Americans (a.k.a. homo technologicus). Since humanity has had no success in voluntarily limiting our population in the past, I fear that continued climate change will lead to food shortages. Hunger and compromised immune systems will lead to disease, war, pestilence, and death.
  • Think about the story of  The Four Horsemen of the Apocalypse as a metaphor for the rather than a Bible prophecy)
    • pestilence, war, famine, death
    • white horse - pestilence (caused by compromised immune systems)
    • red horse - war (the bodies will pile up leading to more pestilence)
    • black horse - famine (will lead to even more war and pestilence)
    • pale horse - death

Links:

• IPCC Special Reports on Climate Change http://www.grida.no/publications/other/ipcc_sr/
  • IPCC Special Report on Emissions Scenarios http://www.grida.no/climate/ipcc/emission/index.htm

  • Emission Scenario	Scenario Story Lines
    A1	http://www.grida.no/climate/ipcc/emission/093.htm#1
    A2	http://www.grida.no/climate/ipcc/emission/094.htm
    B1	http://www.grida.no/climate/ipcc/emission/094.htm#1
    B2	http://www.grida.no/climate/ipcc/emission/095.htm

• What is an Emission Scenario? http://www.manicore.com/anglais/documentation_a/greenhouse/emission_scenario.html
• Google Search (a1 a2 a1 b2 fi emission) http://www.google.ca/advanced_search?q=a1+a2+b1+b2+fi+emission&hl=en
• Wikipedia http://en.wikipedia.org/wiki/Special_Report_on_Emissions_Scenarios
• http://www.climatechoices.org/scenarios.html
• http://www.ipcc.ch/ipccreports/tar/wg2/index.php?idp=154
• http://www.ipcc.ch/pdf/special-reports/spm/sres-en.pdf
• NSR's climate science page