The graph above was plotted using R, from the data available at www.remss.com,
RSS Monthly MSU AMSU Channel TLT Anomalies Land and Ocean v03_3, 3rd column, latitude -70 / 82.5
Global warming doomsayers have been spreading their gospel for many years: emissions from human activities such as industry and car exhaust lead to higher concentrations of CO2 and increase in temperature through the greenhouse effect, and very soon the disastrous consequences will become evident -- or so they claim. However, it is becoming increasingly doubtful whether Nature actually cooperates with the predictions; e.g. data from remote sensing satellite systems show that the troposhere has not warmed as fast as models predict (see remss.com). More headlines can be found easily:
Global Warming has become a religion. Everybody is supposed to believe in global warming caused by carbon dioxide emissions from human activities. The graph below is often shown as proof, and conveniently enough, the instrumental temperature record starts rather late, after the begin of the industrial revolution.
The graph shows changes in global near surface air temperatures . There is an increase starting in the 1920s and 1930s, followed by a decline from the 1940s to the 1970s, and then another increase starting in the 1980s. The general upwards trend looks clear enough. However, looking further back the picture changes:
This graph shows temperature data reconstructed from a number of proxy sources such as tree ring widths, coral growth, and others, shown in different colors . The medieval warm period is also known from a number of anecdotal historic records. If you watch documentaries like The Great Global Warming Swindle you will see another version of this graph where the temperature of the medieval warm period is higher than today's. Note how the choice of the proxy source has a large effect on the results. The black curve is the instrumental record, and the 2004 point is a single unsmoothed value.
For climate studies the time scale of the graph above is rather small. Temperature data reconstructed from Greenland ice cores show that much of the last 12000 years were warmer than today , and temperature changes about as rapid as the recent decades were very frequent.
Looking even further back the picture changes again, this time dramatically . This graph based on ice core data for the past 400,000 years is a favourite of activist Alan Gore. It is supposed to show that increases in CO2 are linked to rises in temperature:
Anyone who has ever done any type of empirical analysis at all knows that graphs can be interpreted in very different ways. The exact processes leading to these data are still very far from clear. However, there are several things that the graph actually shows (note that the time scale is thousands of years ago i.e. today is at the left end of the scale).
In the last couple of decades the CO2 concentration has increased from about 300 ppvm to about 400 ppvm, which is probably due partly to industrial emissions, but also to other activities such as deforestation and burnings of large areas. However, it is far from clear whether this increase in CO2 is actually a bad thing, or whether it has any noticeable effect on the climate. The planet has seen much higher concentrations of CO2 , without the catastrophic consequences that activists like Al Gore would have you believe. On the contrary, life has evolved to the glorious diversity that we see today under very high levels of CO2 for hundreds of millions of years.
In fact, life on earth as we know it would not be possible without CO2. Plants thrive on high concentrations of CO2 since it supplies them with the carbon building block necessary for growth. In commercial greenhouses the CO2 level is artificially increased to achieve higher yields.
Forecasts of the effects of global warming are based on computer models and simulations. Being a computer scientist myself I am keenly aware of the fact that any simulation will yield massively different results depending on the parameters. Add to this the fact that the Earth's climate is an extremely complex process which we are still just beginning to understand, and you can see why I do not put much faith in the accuracy of such models. Only actual data are (moderately) reliable, and those data do not show any warming over the last 15-19 years , depending on the source.
Image from  as slightly modified in . Note (again) that there are several peaks at periods when industrial emissions were neglegible compared to current levels.
Not surprisingly, many climate scientists are nowing trying to 'incorporate' the pause into their models i.e. downplay the importance of those data which so stubbornly refuse to cooperate. Looking at the graph one could expect we are actually entering another cooling phase; that would take a lot of arguing from the IPCC & Co; but no doubt they will be up to the task, since there are also political aspects to consider which contribute to a less than objective treatment of the matter:
As expected, the 2013 IPCC report continues in the same direction, downplaying the pause in warming over the last 15 years. Read the BBC story carefully , there are some interesting points, such as
I wondered how they came up with the 95% figure.
So I read up on the Summary for Policymakers , and there it is at the bottom of page 2:
the following terms have been used to indicate the assessed likelihood of an outcome or a result:
"extremely likely" means 95% or more, "very likely" means 90% or more, and "likely" means 66% or more.
What we see at work here is politics, not science. The situation has been summed up nicely by Maurice Newman in The Australian, January 15, 2014
The IPCC was bound to be captured by the green movement. After all, it is a political body. It is not a panel of scientists but a panel of governments driven by the UN. Its sole purpose is to assess the risks of human-induced climate change. It has spawned industries. One is scientists determined to find an anthropogenic cause. Another is climate remediation. And, naturally, an industry to redistribute taxes to sustain it all. With hundreds of billions of dollars at stake, this cartel will deny all contrary evidence. Its very survival depends on it. But the tide is turning and Mother Nature has signalled her intention not to co-operate.
Here is another quote (in German), from the Austrian Met Office, the Zentralanstalt für Meteorologie und Geodynamik :
Klimavergangenheit - Eine Frage des Maßstabs
Dieser Abschnitt bietet einen Überblick über die abwechslungsreiche Klimaentwicklung im Lauf der Erdgeschichte bis in den Wirkungsbereich des Menschen. Und Klimawandel hat es immer gegeben. So richtig diese Erkenntnis ist, kann sie doch in die Irre führen, wenn man verschweigt, auf welchen Zeitabschnitt, welchen Raum und welches Klimaelement man seine Aussage bezieht. So geht der in Relation zu den letzten Jahrhunderten bedrohlich wirkende Temperaturanstieg seit den 1980er-Jahren in erdgeschichtlichen Zeitskalen völlig unter.
The last sentence roughly translates to: The increase in temperature since the 1980s which seems threatening in relation to the last centuries is completely irrelevant on a geological time scale.
My 0.1% to the debate. Please look at the actual data (if you can find it), try to sort out science from politics, and make up your own mind. Never trust activists or politicians, they have their own agenda, and very little respect for truth.
Johann Mitloehner, 2014-15
Find the RSS satellite data at http://data.remss.com/msu/monthly_time_series/.
https://en.wikipedia.org/wiki/Temperature_record. Image Author NASA, License GFDL;
and Robert A. Rohde, Global Warming Art, License GFDL
see also https://en.wikipedia.org/wiki/File:2000_Year_Temperature_Comparison.png
 https://en.wikipedia.org/wiki/Paleoclimatology. Image Author NOAA, License GFDL
 https://en.wikipedia.org/wiki/Carbon_dioxide_in_the_Earth%27s_atmosphere. Image Global Warming Art, License GFDL