Global Warming Trends

 

The anomaly in the Earth’s temperature based only on thermometers in meteorological stations and excluding the oceans which cover about 70% of the Earth’s surface. The Daily Mail only draw your attention to a small fraction of the data – and they include monthly fluctuations which disguise the clear warming trend.

Why do I ever even look at the Daily Mail website?

The other day I came across this pernicious article purporting to describe a plummeting of global temperatures above the land surfaces of the Earth. The article states:

Global average temperatures over land have plummeted by more than 1C since the middle of this year – their biggest and steepest fall on record. [P.S. by 1C they mean 1 °C not 1 coulomb]

The news comes amid mounting evidence that the recent run of world record high temperatures is about to end.

Some scientists, including Dr Gavin Schmidt, head of Nasa’s climate division, have claimed that the recent highs were mainly the result of long-term global warming.

Others have argued that the records were caused by El Nino, a complex natural phenomenon that takes place every few years, and has nothing to do with greenhouse gas emissions by humans. The new fall in temperatures suggests they were right.

It is accompanied by a misleading graphic:

Graphic from the Daily Mail website. Notice their graph only runs from 1997 and includes large fluctuations due to sub-annual changes. It describes only the changes in temperature above the land surfaces of the Earth.

The article is nonsense from start to finish, but I just thought I would show you how to get at the data for yourself so you can make up your own mind.

Decide for yourself

This excellent NASA web page allows you plot various graphs of temperature data, and change the degree of smoothing applied to the raw data. I invite you to try it out for yourself.

This NASA web page has excellent links and descriptions

You can choose to include land stations only, or combine land and ocean data. Remember that the land surface of the Earth represents less than 30% of our planet’s surface, and so the most relevant measure of global warming involves both land and ocean data.

As well as generating graphs, you can use the website to download data and then graph the data in Excel™ as I have done for the graph at the top of the page.

I don’t fully understand where the data in the Daily Mail graphic comes from. They appear to have picked only recent data and included monthly data rather than annual averages to increase the noise and de-emphasise the obvious trend in the data.

The background colouration in the Daily Mail graphic implies that the high temperatures are all associated with the El Nino conditions. This is not correct. As the graphic below (from skeptical science) shows, years with and without an El Nino are all showing a warming trend.

An animated file showing global surface temperatures in El Nino years, La Nina years, and neutral years.

For the technically-minded reader, this article from Victor Venema may help.

The Trend 

What struck me as shocking was what happened when I set the smoothing of the data to 20 years – so that the trend represented a trend in climate rather than annual or multi-annual fluctuations.

In the figure below I show the data for the land and ocean mean temperature anomaly and the red line shows the smoothing with a 20-year running average. Since 1980 – which was 36 years ago – the data is essentially a straight line.

The estimated change in the temperature of the air above the oceans and the land. The red line shows a smoothed version of the annual data with a 20-year window to reflect changes in climate rather than the internal fluctuations of the Earth’s complex weather systems. Notice that since 1980 , the smoothed line is essentially straight with a gradient of approximately 0.017 °C per year. Source: NASA-GISS: see article for details

What if…

Friends, just suppose that NASA had spotted not a global warming trend, but an asteroid headed straight for Earth. Suppose they calculated it would not destroy civilisation, but it would nonetheless be devastating: its tidal disturbance would cause widespread floods

Would we want to know? Well Yes!

Now suppose that the entire world got together in, say, Paris, and developed a plan to deflect the asteroid. The plan would be expensive and risky – costing about 1% of global GDP – but after about 100 years of effort we would be freed from the risk of a collision.

Would we follow the plan? Well Yes!

Friends, Global warming is equivalent in its impact to an asteroid headed to Earth, and the Paris Accord, while inadequate in itself, represents the start of a plan in which the disparate governments of Earth have agreed to slow development (that brings direct benefit to their citizens) in order to tackle this threat.

Please don’t let the Daily Mail deceive you into thinking global warming is not happening: it is. It is happening slowly – 0.017 °C per year  – and the odd year of inaction makes no difference.

But year upon year of inaction condemns us to a fate that is out of our control.

 

Tags: Climate Change, Daily Mail