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Blog Climate Climate Change Science

Weather, Climate and Chaos Theory

Why is it so hard to predict the weather a week in advance, and how can scientists tell us what they think the climate will be like in 50 years’ time?

First of all, it’s important to understand that weather isn’t random, it’s chaotic. If the weather was random, it would mean there’s no possible way of knowing what it was going to do next. However, the weather does obey the laws of physics and every change in the weather has a cause. The problem is that since there are so many possible causes, we can’t know about them all.

You may have heard of the butterfly effect (first proposed by Ed Lorenz in the 1960s): A butterfly flapping its wings in the Amazon rainforest might, through a long line of unlikely but possible consequences, cause a storm over Texas. In a similar vein, if we don’t know what’s going on in the atmosphere and on the Earth’s surface down to the detail of a butterfly flapping its wings now, we can’t hope to know how that’ll affect the weather in a week’s time. The possible range of consequences grows with time – and the ability to accurately forecast the weather will decrease with time. Of course, some weather situations – such as High pressure, are much easier to predict than others – such as the snow showers which can be caused by Arctic maritime air, but in general tomorrow’s weather forecast is much more likely to be accurate than one for 10 days’ time.

double pendulum

Animation created by Ross Bannister

This animated double pendulum illustrates the chaotic nature of weather really well: The pendulum starts off in the same position, but with a slightly different rotation speed (400.0 degrees/ second v. 400.1 degrees/ second). Over time the difference in the way the double pendulum rotates grows, until the two are behaving completely differently. 

Modern forecasting techniques try to capture the range of possible future weather by making an ‘ensemble’ of weather forecasts – rather than making one forecast with one set of starting conditions (the weather now) they make many forecasts, each with tiny differences in the weather now – trying to take into account the effects of all the possible ‘butterflies’ or other tiny details about the climate system that we can’t possibly measure. The ensemble of forecasts gives forecasters a range of possible weather forecasts, with some indication of what’s most likely, and what might happen.

The climate, unlike the weather, is not chaotic. Remembering that climate is ‘average weather’, if large scale factors which control the climate are known – the composition of the atmosphere, the location of the continents, the Earth’s position in relation to the Sun etc. then it’s possible to predict the climate.

In between weather forecasts and climate forecasts come seasonal forecasts – the ‘what will the weather be next winter’ type questions. As the weather is chaotic, this is very hard to do, but there is some skill to be found in looking at the large scale influences on the weather – for example, if there’s a strong El Niño occurring, then certain weather patterns are more likely to form than others.

The North Atlantic Oscillation (or NAO) is another of the many factors which can be looked at. Meteorologists look at the pressure difference between Iceland and the Azores. The pressure is always lower in Iceland than in the Azores because of the large scale circulation of the atmosphere, however the difference in pressure can vary. A large difference in the pressure (a positive NAO) leads to stronger westerlies, bringing moist air to Europe. Consequently, summers are cool and winters are mild and wet in Central and Western Europe. In contrast, if the pressure difference is small (a negative NAO), westerlies are suppressed, winters are cold and dry in northern European areas and the depressions track southwards toward the Mediterranean Sea, bringing increased storm activity and rainfall to southern Europe and North Africa.

Categories
Blog Climate Climate Change Science

Carbon Dioxide in the Atmosphere – Balancing the Flow

It is the concentration of greenhouse gases in the atmosphere, rather than the emissions at a particular moment in time, which determines the temperature of the Earth.

How the concentration of Carbon Dioxide changes is determined by the balance between the amount of carbon dioxide going in to the atmosphere, and the amount being taken out. Change the flow rate using the + and – buttons on the animation below, where the water level in the bath represents the concentration of greenhouse gases in the atmosphere. 

In the furthest left position, there is less (no) carbon dioxide being added to the atmosphere than is being taken out by natural and human processes. The concentration of carbon dioxide in the atmosphere falls.

In the second position, the same amount of carbon dioxide is being added to the atmosphere than is being taken out by natural and human processes. The concentration of carbon dioxide in the atmosphere stays the same.

In the third position, there is slightly more carbon dioxide being added to the atmosphere than is being taken out by natural and human processes. The concentration of carbon dioxide in the atmosphere rises.

In the fourth position, there is much more carbon dioxide being added to the atmosphere than is being taken out by natural and human processes. The concentration of carbon dioxide in the atmosphere rises rapidly.

Even if emissions fall (position 3), as was the case briefly in 2020 when COVID19 related restrictions reduced global emissions, the concentration of greenhouse gases in the atmosphere continues to rise.

The relationship between emissions, concentrations, global temperature and sea level

Reducing emissions

Even before humans were around, there was a constantly evolving balance of greenhouse gases in the atmosphere. Natural sources, such as respiring animals, the decomposition of organic matter, volcanoes, rock weathering, freshwater outgassing and ocean-atmosphere exchange of gases are balanced by photosynthesis and ocean-atmosphere exchange of gases.

Humans have added additional sources and sinks, as are summarised by this diagram from the IPCC:

WG1 Chapter 6, figure 1. The numbers represent carbon reservoirs in Petagrams of Carbon (PgC; 1015gC) and the annual exchanges in PgC/year. The black numbers and arrows show the pre-Industrial reservoirs and fluxes. The red numbers and arrows show the additional fluxes caused by human activities averaged over 2000-2009, which include emissions due to the burning of fossil fuels, cement production and land use change (in total about 9 PgC/year). Some of this additional anthropogenic carbon is taken up by the land and the ocean (about 5 PgC/year) while the remainder is left in the atmosphere (4 PgC/year), explaining the rising atmospheric concentrations of CO2. The red numbers in the reservoirs show the cumulative changes in anthropogenic carbon from 1750-2011; a positive change indicates that the reservoir has gained carbon.

IPCC, 2013: Climate Change 2013: The Physical Science Basis. Working Group I Contribution to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

More processes could be added to this picture in the future, such as carbon capture and storage.

This animation was adapted from an infographic produced by the IPCC https://www.ipcc.ch/sr15/mulitimedia/worlds-apart/

Other related links

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Science

Short Atmospheric Physics Videos

We have been delighted to work together with Imperial College, London and the Institute of Physics Environmental Physics group to produce a set of 6 short films looking at how we can use an infrared camera or thermometer to observe physics at work in the atmosphere.

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Science Weather

Coriolis Effect Film

We are delighted to announce a new and exciting short animation explaining the physics behind the Coriolis Effect.

The film can be found on our In Depth – the Coriolis Effect page.

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Climate Change Primary Science Teaching

Post SATs Year 6 Weather and Climate Day

We have pulled together a set of Weather and Climate resources which could be used with a year 6 class after their SATs exams. Designed as a progressive set of engaging and interactive resources, they introduce skills and knowledge which will help prepare students for secondary school.

The resources can be used in independent lessons, or as part of a whole or half weather and climate themed day.

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Climate Change Geography Research Science

Tree Ring Resources

We were delighted to launch our past weather and climate teaching resources at the Geographical Association’s meeting in Manchester last week.

You can find the introductory film, online game and teaching resources here

We’ll add more background information and some instructions about how to make a replica of the amazing tree ring jigsaw in lego or even by 3D printing it, shortly.

resources
Categories
Climate Research Science

How does the Earth’s energy budget compare to other planets?

This article, just published in Physics Review, compares the flows of energy in the Earth’s atmosphere to those of Mars, Venus, Titan and Jupiter.

Read the whole article here.

Earth
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Research Science

Near Total Solar Eclipse, 20 March 2015 – The National Eclipse Weather Experiment

eclipseMarch 2015 Near Total Solar Eclipse – The Science and Folklore behind Eclipses
On the morning of Friday 20 March 2015 there will be a rare near-total solar eclipse visible from the UK. The Department of Meteorology at the University of Reading are holding a series of events as part of National Science Week to explain the science and folklore behind this natural phenomenon, and the weather changes that may accompany it.

Thursday 19 March 2015 – Open Evening
19:00 – 21:00 in The Madjeski Lecture Theatre, Agriculture Building, University of Reading
On the evening before the eclipse we will be holding an open evening, which will include talks on:
Space Weather
Eclipses – The Science
Eclipses Throughout the Ages
We will also be opening up our laboratories for demonstrations using meteorological equipment and sensors to take observations of the expected variations in temperature and wind speed accompanying the eclipse.
The event is free of charge, but places are limited. Please contact Dawn Turner to register if you would like to join us.

Friday 20 March 2015 – NEWEx – National Eclipse Weather Experiment
08:00 – 11:00 Department of Meteorology, University of Reading
A solar eclipse briefly dims the radiation coming from the Sun, leading to cooling in the atmosphere with interesting effects on the weather. To study these effects, the Department of Meteorology invites you to take part in NEWEx – National Eclipse Weather Experiment, a citizen science project to collect weather data during the solar eclipse for detailed analysis. We welcome participation and lesson inclusion from schools across the country.

Eclipse 2015 – notes for schools
National Eclipse Weather Experiment Frequently Asked Questions (FAQs)

Categories
Science

Build a weather satellite in Minecraft?

minecraft

EUMETSAT is launching a Minecraft satellite-building competition for 6-16 year olds this week.

The aim of the competition is to get competitors to build a model of one or more of EUMETSAT’s weather satellites in Minecraft, or to be creative and design their own satellite from scratch. The closing date of the competition is April 30 2015.

All entries will be displayed on the EUMETSAT Learning Zone website and the winners of the two categories will each get Lego Mindstorms. There will also be runners-up prizes of Raspberry Pi (mini PC) starter kits.

More information about the competition is available on EUMETSAT’s Youth Education website at: l-zone.info/minecraft-competition-2015.

EUMETSAT operates Europe’s weather satellites, including Meteosat-7, 8, -9 and -10 and Metop-A and –B. Find out more at: www.eumetsat.int.

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Geography Science Secondary Teaching

Climate Change Updates for Science and Geography Teachers

Together with climate scientists from the National Centre for Atmospheric Science, we have compiled two booklets based on the latest Intergovernmental Panel on Climate Change (IPCC) report. The contents have been chosen to support the new National Curriculum in England. The booklets can be found on the MetLink site, under the climate tab, and are available for science and geography or, to request a print copy, please contact education@rmets.org