Understanding Climate Change #1

Last week I signed up for an online course about the challenges and solutions of climate change run by the university of Exeter. I’m making a series of blog posts on it as per their recommendation so I can share the knowledge with everyone even if you haven’t signed up. Most of the information below comes directly from the videos and articles they have provided so if there are things you think I haven’t explained well enough, go and sign up for free and take a look for yourself.

As expected, the first week went through some of the basics and provided an introduction to some of the key concepts that are to be explored as the course progresses. If you already know the basics you can skip to the end to find a short summary of everything that was covered.

Analogies

We’ve all heard of the greenhouse effect as an analogy of the of the warming effect that greenhouse gasses have on the Earth. The first section of the week looked at whether or not this was an appropriate way to view what happens. The only real flaw is that in a greenhouse, temperature increase is a result of a lack of air flow stopping the escape of heat through convection. This isn’t the case for the Earth, where certain molecules (known as greenhouses gasses) absorb infrared radiation and re-emit some of it back to the Earth’s surface. You can think of the molecules forming a blanket around the Earth, keeping it warm.

Is the greenhouse model a bad one? No of course not. It has the advantage of being easy to understand and even though many people haven’t learnt the science behind it, it is effective at getting the message across. Feel free to carry on using it.

One point to mention is that carbon dioxide is NOT the main contributor to the greenhouse effect. That title actually goes to water due to its high abundancy. It’s also part of an important feedback loop. Other greenhouse gasses include methane, nitrous oxide and CFCs.

Climate systems

Anyone who paid attention in high school geography knows the difference between weather and climate – climate relates to how the weather changes in the long term.

Something I expect to become increasingly evident during the course is just how incredibly complex the climate system is. The statistical models we build to try and predict the climate and its effects are way beyond my understanding. There are so many factors influencing the Earth’s climate and that makes predictions difficult.

Water vapour feedback

Feedbacks play a key role in the state of the climate system and explain how our climate is able to ‘self-regulate’. One of these is the water vapour feedback I mentioned.

  1. Radiation causes the evaporation of water. This resides as a gas in the atmosphere.
  2. Water vapour in the atmosphere absorbs radiation from the Earth. This is re-emitted and some returns to the Earth’s surface causing more warming.
  3. Increased warming causes more evaporation.

See how it’s a vicious cycle? The feedback is positive because it acts to amplify the changes that occur.

15.2

Ice albedo feedback

Albedo is a term I hadn’t heard before, although the concept is one I knew of since watching ‘The Day After Tomorrow’. It is the focus of the second feedback loop and concerns sea ice. When you compare ice and sea, obviously the ice is much more reflective than the sea so more ice means more reflection and less warming. However, when warming does occur and the ice melts more radiation is absorbed by the sea and hence more warming occurs, melting more ice.

As an extension to this some scientists worry that the melting Arctic sea ice will deposit so much fresh water into the sea that it will interfere with ocean currents like the North Atlantic Current, triggering a ‘deep freeze’ over North America and Western Europe. It was predicted that this was a possibility within 20 years (that prediction was over 12 years ago). What’s clear is that the Arctic is currently warming up twice as fast as the global average, which is bad news.

Planck feedback

While the two feedbacks above are examples of positive feedback, Planck feedback falls into the negative feedback category. It’s a concept most people will be familiar with. As the surface temperature of the Earth increases the amount of infrared radiation it emits also increases. This loss of energy causes the temperature of the Earth to decrease.

Summary

There is a lot to learn about climate change and this week’s introduction has provided the basics on climate analogies, models and systems. As a short summary:

  • The climate system is incredibly complex and is influenced by many factors.
  • The greenhouse analogy for the warming of the planet may be better explained by the ‘blanket’ analogy.
  • Water vapour is the main contributor to the greenhouse effect. Other greenhouse gasses include carbon dioxide, methane, nitrous oxide and CFCs.
  • Feedbacks play a key role in the state of the climate system. Examples include water vapour, ice albedo and Planck feedbacks.

Since it’s the first week there shouldn’t be any difficulties in terms of understanding. I’m sure these topics will be revisited later on so we can deepen our knowledge. How deep you ask? Well there’s only so far you can go into a subject while on a free eight-week course but my first impressions are very positive. I’m always eager to learn more and while I already have a good understanding of some of the course content I realise there is still a lot to learn.

As I said before I believe you can still sign up, I mean it’s free so you have nothing to lose. The more people who understand climate change, the more likely we are to save the planet right?

Some excellent resources were highlighted this week including the NASA: Climate Change website and Climate&Us, which provides up to date news and articles. Feel free to check them out before part two rolls around.

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Jack Nokes Written by:

Environmentalist and engineering student.