Week 2 - Past Climate Change

Ok so i've now progressed into the second week of this course, got 14 out of 15 in the test...get in! I have made some connections and read other peoples blog etc so progress is being made. There are some really interesting people on this course who I can definitely learn from.

Past climate change

For 4.5 billion years the Earth has been self regulating and pretty much habitable for most of that time. Throughout these years there have been some positive and negative feedback loops which have impacted the Earths climate.

The ageing sun

As the sun gets older it gets hotter and hotter but luckily enough the Earth is located in the area around the sun which is neither too hot nor cold so is called the habitable zone. Either side of us is Mercury (nearest the sun) which is so hot is can melt lead, and on the other side (further away from the sun) is Mars which is frozen.

At the birth of our solar system, blooming ages ago, the sun was a good 30% brighter than it is now which would mean that the Earth would be 20 degrees cooler meaning it would have been frozen....but it wasn't. The reason for this is because the cuddly 'blanket' around the Earth was much thicker and contained a lot more CO2 then there is now which kept the Earth nice and warm and habitable. 

Nowadays the blanket is no longer as thick (which is pretty good as we would very toasty indeed) but the question is where has all the CO2 gone? This can be explained through chemical weathering. Chemical weathering is where carbon dioxide and rainwater forms a weak acid, carbonic acid, that dissolves silicate rocks. The carbon in the form of bicarbonate ions washes into the ocean, where it is used by many organisms to form their shells, which are then deposited on the ocean bed to form carbonate rocks.

1. Carbonate rocks are a class of sedimentary rocks composed primarily of carbonateminerals. The two major types are limestone, which is composed of calcite or aragonite (different crystal forms of CaCO₃) and dolostone, which is composed of the mineral dolomite (CaMg(CO₃)₂).

So the Earth self regulated itself through negative feedback - Sun got hotter, more chemical weathering occurred and the Earth stored more carbon which then reduced the amount in the blanket.

Snowball Earth

Another thing that happened over the course of these past 4.5 billions years has been 5 times occasions where it has got pretty cold which we call the Ice Ages, during these times there were still parts of the Earth that were not completely frozen. However, there was a time when the Earth did completely freeze over which is affectionately known as Snowball Earth.

Snowball earth describes the coldest global climate imaginable - a planet covered by glacial ice from pole to pole. The global mean temperature would be about -50°C (-74°F) because most of the Sun's (Solar) radiation would be reflected back to space by the icy surface.  The last snowball earth ended 635 million years ago (Ma), near the end of the Proterozoic Eon.  

Here is my interpretation of the Snowball Earth and the process of how it cam about. My 30 minute stab at creating something understandable with a vague artistic flare - definitely needs more work but it gives you that jist of things!

Understanding factors which cause climate change

There are a number of natural variations which contribute to changes in the Earths climate which fall into two categories; predictable and unpredictable.

Predictable
There are 3 predictable variations which are linked to the the way the Earth moves around the sun

• Eccentricity - the Earth's orbit is changing from a circular one to a more elliptical
• Obliquity - The tilt of the Earths axis varies
• Precession - Where the Earth wobbles like a spinning top (over a period of 23,000 yrs)

Unpredictable

• Volcanoes - eruptions cannot be planned and when they do they reduce the Earth's temperature but emitting aerosols into the atmosphere which reflect solar radiation back towards the sun
• Solar variability - the change in the amount of radiation emitted by the Sun

Climate change records

In order to understand climate change and to reconstruct the past changes we need date. Unfortunately we have only been collecting instrumental data and making visual records in the short term (post 1600) but we need to know what happened prior to that. Current instrumental data includes weather stations, weather balloons, satellites, ocean monitoring and prior to that ships made diary entries which have been put onto databases.

How do we find data prior to 1600? Well this lies in proxy data which are preserved physical characteristics of the environment that can stand in for direct measurements. We can obtain proxy data from tree rings, ice cores, fossil pollen, ocean sediments, corals and historical data.

Tree rings

In the spring time, through photosynthesis trees begin to grow. Trees generally produce one ring per year. During a good year the tree grows faster and so lays down more tissue in the year, resulting in a wider growth ring. Poor conditions mean slower growth, less tissue laid down and consequently a narrower ring. 

Tree rings are a great way of seeing what the climate conditions were on Earth going back hundreds to thousands of years...depending on the tree of course. It is important to apply the principle of cross dating, a tree may have become affected by disease or may have consumed more nutrients if a nearby neighbour has died. So a number of trees in an area can be looked at as they will depict the same patterns over time. Scientists can also over lap existing tree rings with those from fallen trees from a similar area so they can gather information even further back in time.

What effect do Volcanoes have on climate change?

When a volcano erupts it emits lots of aerosols which suspend in the stratosphere and reflect solar radiation which therefore cools the Earth. The aerosols are suspended for approximately 1-2 years and they then fall to Earth. Their impact is short term but does have a considerable cooling effect.

As well as aerosols, volcanoes emit CO2 as well as other greenhouse gases which contribute to the blanket surrounding the Earth which warm it up. These remain in the atmosphere for a longer time so after the cooling will contribute to the warming of the Earth again.

Reflection from this weeks course

• What are the most important themes you have learned this week?

Snowball Earth, proxy data and volcanoes

• What aspect of this week did you find difficult?

Understanding the ever changing climate changing and where we fit in to the changes today. It's pretty hard to understand that the Earth warms and cools due to lots of natural variations and then think that we will be the cause of it warming further, especially as people post youtube videos which argue against it.

• What did you find most interesting? And why?

Snowball Earth and how the Earth completely froze over when it usually self regulates itself  through natural feedbacks/variations.

• Was there something that you learned this week that prompted you to do your own research?

Understanding tree growth and photosynthesis as this is something I hadn't touched on for a long time also the understanding behind the snowball earth.

Further links and websites:
Ageng sun - http://tvblogs.nationalgeographic.com/2010/07/21/hotter-and-hotter/

Snowball Earth - http://www.snowballearth.org/index.html

BBC Snowball Earth transcript- http://www.bbc.co.uk/science/horizon/2000/snowballearth_transcript.shtml
Realtime board site - https://realtimeboard.com/app/76978440/Snowball-Earth---Charly-style/
Tree rings - http://www.rsc.org/Education/Teachers/Resources/jesei/treering/home.htm
Proxy data - http://www.ncdc.noaa.gov/news/what-are-proxy-data

Week 1 - Starting off the course and the background behind climate change

Oh blimey, when they said an online course I just thought it would be all watch a video here, read an article there... I didn't expect there to be social media interaction and the  need for a blog. However, I am not one to shy things off likely especially when social media is involved. I am what you call a social media whore, which my girlfriend mentions on a daily basis, so I am happy to oblige.

Right then here I go with the blog. This is collection of bits and bobs I've learnt from Week 1...

Introduction

Greenhouse effect and the Earths little cuddle blanket

The greenhouse effect is not a good metaphor but everyone seems to be using it!

Effectively, the suns rays come in as long waves hit the earth and reflect as short waves (infrared heat). However, the waves going out don't just disappear into space, they get absorbed by gas in the atmosphere, which are called green house gases (GHG)

The reason that the green house analogy isn't suitable is because the gases really work as a blanket around the earth, keeping the warmth from the person (earth) escaping but also returning the heat back to the person (earth) to keep them warm.

The heat that gets reflected back from the gases is called Albedo:

1. Albedo is the fraction of solar energy (shortwave radiation) reflected from the Earth back into space. It is a measure of the reflectivity of the earth's surface. Ice, especially with snow on top of it, has a high albedo: most sunlight hitting the surface bounces back towards space.

The albedo is all dependent on the earths surface; Ice and snow will reflect more light (high albedo) where the dark ocean will reflect less (low albedo).  The earth reflects 30% of sunlight and 70% is absorption  - so the gases around the earth maintain a temperature of 15 degrees Celsius.

Some gases in the atmosphere are long-lived and remain semi-permanantly in the atmosphere and they do not respond physically or chemically to changes of temperature so these are 'forcing' clime change. Other gases such as water vapour do change and tare called feedbacks.

The gases which contribute to the greenhouse effect are:

• Water Vapour - most abundant, increases as temp of Earth warms which increases clouds and precipitation
• Carbon Dioxide (CO2) - minor components of the atmosphere but most important long-lived gas forcing climate change.
• Methane - more active then CO2 but less abundant
• Nitros Oxide - one of the most powerful GHG
• Chlorofluorocarbons (CFC's) - have the ability to destroy the ozone layer

Weather and Climate

Some people get a little confused about which is which, so here is a brief description of each:

Weather

Elements which we see daily such as temperature, rainfall, wind, snow and which change on a daily basis.

The weather takes into account the temperature, precipitation, humidity and atmospheric pressure of the part of atmosphere (air) closest to the surface of the earth.

The weather is constantly changing as temperature and humidity change in the atmosphere. Landmasses, such as the British Isles, experience constantly changing weather conditions.

Climate

Climate means the average weather conditions in a particular location based on the average weather experienced there over 30 years or more. Global climate zones with similar flora, fauna and climate are called biomes.

Climate refers to what is expected to happen in the atmosphere rather than the actual conditions. It is possible for the weather to be different from that suggested by the climate.

Feedbacks and cycles

There are 5 different elements of the climate system:

• Atmosphere
• Hydrosphere
• Biosphere
• Cryosphere
• Lithosphere

Feedbacks operate in the climate system which are a closed loop of cause and effect.

There are 3 keys feedbacks systems effecting climate change:

Water vapour - temperature rise, increase evaporation which increases water vapour which increases temperature and on and on. This is a positive feedback.

Ice albedo - Suns rays come down and get reflected by the ice and absorbed by the ocean, as the ocean absorbs the heat the ice melts which increases the ocean surface area and increases the temperature of the earth which means more ice is melting. Negative feedback.

Radiation - All objects give off radiation but the warmer the object the higher the radiation and the more radiation given off in heat energy the cooler it becomes, this happens in the use of coal as a fuel. Plank feedback as described by the guy who discovered it. Negative feedback.

The climate system self-regualtes through negative and positive feedback systems.

Negative feedback — this is an impact which offsets the prevailing change in climate. Under global warming, this would create a cooling effect, balancing out the changes. If the climate was getting colder, it would create a heating effect.

Positive feedback — this is an impact which increases the change in the climate. It would add to global warming by creating further heating or, if our climate was cooling, would cool the climate further.


IPCC (Intergovernmental Panel on Climate Change) - this is the leading inter nation body for assessing climate change. It was established in 1988 by the United Nations Environment Programme (UNEP) and the World Meterogical Organisation (WMO). Thousands of scientists around the world contribute on a voluntary basis.

My reflections on the first week:

What are the most important themes you have learned this week?

The science behind climate change and the various systems involved.

What aspect of this week did you find difficult?

Feedbacks and understanding positive and negative feedbacks

What did you find most interesting? And why?

Climates and weather systems and everyones descriptions of then on the course.

Was there something that you learned this week that prompted you to do your own research?

Only to look up what things actually mean such as scientific words I had never heard of such as albedo, lithosphere and what climate and weather actually was.

Are there any web sites or other online resource that you found particularly useful in furthering your knowledge and understanding?

Nasa website: climate.nasa.gov/causes/
Earth and Space research: www.esr.org
Met Office www.metoffice.gov.uk
http://www.bbc.co.uk/schools/gcsebitesize/geography/weather_climate/climate_rev1.shtml


Phew. Week one done. Over and out...