Herald Sun War on Science: manipulating graphs to “hide” global warming

What, no warming?

We know images are powerful, and that they can often convey information in a way that words often fail to do. Especially when it comes to an area as complex as climate science.

But what if the images being used to communicate the science are either wrong or deceptive?

A recent example of this comes via Andrew Bolt’s blog today, who reports that for “fifteen years there’s been no warming”:

The inconvenient truth cannot be ignored much longer: 

The supposed ‘consensus’ on man-made global warming is facing an inconvenient challenge after the release of new temperature data showing the planet has not warmed for the past 15 years… 

Based on readings from more than 30,000 measuring stations, the data was issued last week without fanfare by the Met Office and the University of East Anglia Climatic Research Unit. It confirms that the rising trend in world temperatures ended in 1997.

Bolt displays the above graph as “proof” there has been no warming.

The source of this recent claim comes from an article by one David Rose of the UK’s Daily Mail:

The supposed ‘consensus’ on man-made global warming is facing an inconvenient challenge after the release of new temperature data showing the planet has not warmed for the past 15 years.

The figures suggest that we could even be heading for a mini ice age to rival the 70-year temperature drop that saw frost fairs held on the Thames in the 17th Century.

Based on readings from more than 30,000 measuring stations, the data was issued last week without fanfare by the Met Office and the University of East Anglia Climatic Research Unit. It confirms that the rising trend in world temperatures ended in 1997.

It’s an impressive looking graph and remarkable claim– but can it be true?

Has warming stopped?

In reality, both the graph and the manner in which Rose has framed the article is misleading.

What a tangled web we weave, when we make graphs to deceive

Firstly, note the “X” axis, that shows average global temperatures ranging between the very narrow band of14.2 and 14.6 degrees Celsius.

What the Daily Mail fails to tell you is that the baseline temperature for the globe is calculated at 14.0 °C, as the Met Office notes.

They then added the temperature anomalies to that baseline figure.

For those not familiar with the concept of temperature anomalies, scientists calculate an average temperature as a “baseline” and then measure temperatures that depart from that:

The term temperature anomaly means a departure from a reference value or long-term average. A positive anomaly indicates that the observed temperature was warmer than the reference value, while a negative anomaly indicates that the observed temperature was cooler than the reference value.

The Daily Mail has done a simple act of arithmetic, and added:

Baseline + temperature anomaly = yearly average

Thus for the year 2000 the average global temperature was 14.52 °C, or:

14°C + 0.52°C = 14.52°C

Strangely the Daily Mail is silent on this fact.

There is no mention of temperature anomalies.

Fortunately the Met Office makes those figures available in a table ranking the “top 12” hottest years since 1998:

The table ranks the “top 12” warmest years since 1998 and cites figures from the NASA, the World Meteorological Organisation among others.

The figures clearly show the globe is warming, not cooling. While 1998 remains the “hottest” year on record, we’ve seen successive years of rising temperatures.

Too short time frame: reproducing the Daily Mails cherry picked graph

As many of you would have already guessed the time frame chosen by the Daily Mail – 1998 to 2012 – is too short.

Using the same “methodology” (and the above data), I was able to produce a similar graph showing a “decline” in temperatures:

Look at that! Temperatures are in decline since 2001!

All I did was add the baseline figure with the temperature anomalies – and used a truncated time series – and presto!

Science is hard work, and I’d never pretend I’d just falsified climate change.

Producing drivel like the Daily Mail has is easy – but sadly such material is all too effective in it ability to deceive.

How it’s really done…

In order to get a better understanding of long term temperature trends, you need to exclude the baseline temperature and then plot the anomalies over a much longer period of time.

NASA does it right:

…which clearly shows warming.

I use it to illustrate the difference just how deceptive the Daily Mail’s graph is. But somehow I don’t think it was created with the best intentions.

The Met Office strikes back

The Met office has responded to the article as well, calling out Rose on his misrepresentations:

This article includes numerous errors in the reporting of published peer reviewed science undertaken by the Met Office Hadley Centre and for Mr. Rose to suggest that the latest global temperatures available show no warming in the last 15 years is entirely misleading.

Despite the Met Office having spoken to David Rose ahead of the publication of the story, he has chosen to not fully include the answers we gave him to questions around decadal projections produced by the Met Office or his belief that we have seen no warming since 1997.