For many approaching the climate debate it is a huge shock to find out how much our climate has varied in the past.
Even Prince Charles is allegedly confused about it:
Well, if it is but a myth, and the global scientific community is involved in some sort of conspiracy, why is it then that around the globe sea levels are more than six inches higher than they were 100 years ago?
Comical (and my sincere apologies to the Prince if he has been misquoted by the UK media), but unsurprising – as most people really have no idea.
Take a look at An Inconvenient Temperature Graph if you want to see how the temperature has varied over the last 150,000 and the last million years. And one graph reproduced here:
The last million years are incredible. Sea levels – as best as we can tell – have moved up and down by at least 120m, possibly more.
There are two ways to think about these massive changes. Interesting how the same data can be interpreted in such different ways..
The huge changes in past climate that we can see from temperature and sea level reconstructions demonstrates that climate always changes. It demonstrates that the 20th century temperature increases are nothing unusual. And it demonstrates that climate is way too unpredictable to be accurately modeled.
The huge changes in past climate demonstrate the sensitivity nature of our climate. Small changes in solar output and minor variations in the distribution of solar energy across seasons (from minor changes in the earth’s orbit) have created climate changes that would be catastrophic today. Climate models can explain these past changes. And if we compare the radiative forcing from anthropogenic CO2 with those minor variations we see what incredible danger we have created for our planet.
We will try and understand the ghosts of climate pasts in future articles.
Articles in this Series
Part Two – Lorenz - one point of view from the exceptional E.N. Lorenz
Part Three – Hays, Imbrie & Shackleton - how everyone got onto the Milankovitch theory
Part Four – Understanding Orbits, Seasons and Stuff - how the wobbles and movements of the earth’s orbit affect incoming solar radiation
Part Five – Obliquity & Precession Changes - and in a bit more detail
Part Six – “Hypotheses Abound” - lots of different theories that confusingly go by the same name
Part Seven – GCM I - early work with climate models to try and get “perennial snow cover” at high latitudes to start an ice age around 116,000 years ago
Part Seven and a Half – Mindmap - my mind map at that time, with many of the papers I have been reviewing and categorizing plus key extracts from those papers
Part Eight – GCM II - more recent work from the “noughties” – GCM results plus EMIC (earth models of intermediate complexity) again trying to produce perennial snow cover
Part Nine – GCM III - very recent work from 2012, a full GCM, with reduced spatial resolution and speeding up external forcings by a factors of 10, modeling the last 120 kyrs
Part Ten – GCM IV - very recent work from 2012, a high resolution GCM called CCSM4, producing glacial inception at 115 kyrs
Pop Quiz: End of An Ice Age - a chance for people to test their ideas about whether solar insolation is the factor that ended the last ice age
Eleven – End of the Last Ice age - latest data showing relationship between Southern Hemisphere temperatures, global temperatures and CO2
Twelve – GCM V – Ice Age Termination - very recent work from He et al 2013, using a high resolution GCM (CCSM3) to analyze the end of the last ice age and the complex link between Antarctic and Greenland
Thirteen – Terminator II - looking at the date of Termination II, the end of the penultimate ice age – and implications for the cause of Termination II