Just how much has the world really warmed in the last century or two?  The above plot shows one of the longest available historic temperature records available.  Here we see that Northern Ireland warmed at the rate of 0.6 deg.C / 100 years.  The trend is linear without any sign of a "hockey stick" and, being an island, is probably representative of ocean temperatures.  The oceans contain about 15 times as much thermal energy ("heat" energy) as the land surfaces, so ocean temperatures are a better indicator of climate change.  Land measurements are subject to urban crawl - registering faster increases because of the spread of buildings, roads, air strips etc.  So have a look at these sea surface temperatures ...
The world is heading for cooling ....
Copyright: Douglas J Cotton, 10 September 2011.  Updated 14 April 2014

Decline has continued - click here.
Plot by Trenberth appearing on Skeptical Science
This plot is for the Arctic from 1880
to 2004.  It also shows even higher
temperatures between 1935 and
1945, but then cooling after WWII.
This paper discusses why carbon
dioxide could not have been the
cause.  Note also the 4 degree rise
between 1919 and 1939.  Read here
why natural cycles control the Arctic. 
For more detail read this article. 
Nor is the Antarctic warming recently.

With the publication of this paper (September 2011) we can see that a valid, repeatable atmospheric experiment shows that the atmosphere is generally cooler than the surface, and it cools at a faster rate at night.

The whole greenhouse effect argument hinges upon whether or not the infra-red "back radiation" coming from greenhouse gas (GHG) molecules and heading for the oceans or land actually transfers thermal energy to the surface.  There has never been, and never will be any empirical evidence that such is the case.  Indeed, Prof. Nahle has postulated in the above paper that it most certainly is not the case.  Furthermore, standard physics can be used to prove that such radiation from a colder atmosphere cannot transfer additional thermal energy to a warmer surface.  The radiation is rejected and, in effect, resonates and is then scattered off the surface without leaving any energy behind.  There is more radiation coming out of the warmer surface and it is rather like directing a fire hose at a garden hose.   Prof. Claes Johnson decribes the process like this.  I refer to it as "resonant scattering" in my publication entitled Radiated Energy and the Second Law of Thermodynamics.

If you have a background in physics and wish to look into this further, I suggest you read the above paper (available March 13, 2012) and feel free to email me with any genuine enquiries related to its content.  See also the Radiation page here which explains in more detail.

So, in effect, when carbon dioxide captures radiation it will very quickly radiate again with equal or lower energy.  The energy involved will transfer in and out of numerous GHG molecules moving around in a random fashion.  Hence, some will end up getting to space and some will approach the Earth, but get "bounced" off.  So the surface molecules are just like air molecules in that regard.  Hence the energy involved only has one permanent "end" to its zig-zag path and that is to space.  One can liken it to a pool table, without pockets, but with one end removed so that balls bounce around until they fall on the floor.

One other interesting fact is that direct incident solar radiation contains plenty of energy in the infra-red band and, when observed from the Earth, it is quite clear that water vapour and carbon dioxide have absorbed some of this IR radiation on its way to Earth, and sent some back to space, thus preventing some warming.  (See this plot.)   I wonder why they never talk about this cooling effect of carbon dioxide?

The reality is that we can now see slight cooling ahead.  The steep rising trend in temperatures flattened around 2001 to 2002 and hit a maximum in about 2006 as shown above.  The sea surface temperatures have now started to decline, as have sea levels. Trends should be curved lines (as at the foot of the page) not straight lines, and natural cycles are evident. 

Just because temperatures rose a fair bit between 1975 and 2008 at the same time that carbon dioxide levels also rose does not prove that carbon dioxide was the cause.  There were similar rises of about 0.5 degrees between 1909 and 1942 when there was far less carbon dioxide in the atmosphere.  (See this plot.)  There are other possible natural causes which could be associated with natural variations in cloud cover or in thermal energy generated under the surface.

This may help you to understand the process:  even just 100 metres underground the temperature is very stable over the course of hundreds of years.  As you come closer to the surface you will observe slight variations between summer and winter, but not much.  Of course you will see daily variations just a few centimetres down, but, overall, the stable temperatures underground (which have been established over billions of years primarily as a result of heat generated underground) will tend to control climate.  You can draw an analogy with a small glass of water in a large air-conditioned room.  The temperature of the water (representing the oceans and land surfaces) will be controlled by that of the air which represents the far greater thermal energy in the rest of the Earth under the surface.  

The atmosphere acts as a "dam" so that the surface does not cool at night as much as that on the Moon.   The effect of that dam depends on the rate at which thermal energy can escape to space by both radiation and convection, the latter involving physical upward movement of warmer air.  This rate is in turn a function of pressure which itself depends on the weight of all the molecules in the air.  Less than 1 in 2,500 of these are carbon dioxide, so its weight will have very little overall effect.

You can see the effect of pressure on heat transfer rates in the atmosphere if you note that, in the lowest 11Km of the troposphere the temperature falls by about 68 degrees C, whereas in the next 10Km it falls only about 12 degrees.  Under the surface it can fall by over 250 degrees in the outermost 10Km of the crust.

At the interface of the surface and the atmosphere air molecules collide with those of the surface and, as a result, thermal energy is transferred from the warmer molecules to the cooler ones.  Temperature equilibrium is achieved (at least in calm conditions) by this conduction-like process between a gas and a solid surface, the process usually being called diffusion.  The part played by radiation depends on the properties of the surface at any particular point, as well as the difference in temperature.  But note that there must be a significant amount of diffusion to cause the observed temperature equilibrium between the surface and the first millimetre or so of the atmosphere.   This paper shows one calculation in which loss by "convection" was "four-thirds" that by radiation, but three times as much with wind.

It is totally inappropriate to consider only that thermal energy which is transmitted by radiation, whilst ignoring diffusion (molecular collision) and convection processes, but it is worth noting that greenhouse gases are the very ones which can cool the atmosphere by radiating thermal energy away, unlike oxygen and nitrogen.   Here we read "The exchange of vibrational energy between O2 and the CO2 levels can be important for the de-excitation of O2."

Extra radiation sent back to Earth by carbon dioxide does not remain as extra thermal energy in the land and oceans or the atmosphere.  It cannot be absorbed at all because it has lower energy than the radiation being emitted.  
(You may read more about the physics involved on this page on my other site.  For those who understand physics read this and this.)  Even the magnitude of such radiation may be overstated:  you will note in this paper that some estimates used by the IPCC claim that the total emittance of carbon dioxide is 5.35 W/m^2 whereas standard physics shows it could not exceed 0.9 W/m^2.

There is a good explanation of the role of radiation in "heat" transfer in item 2.2 at this site.  Molecular collision can transfer some thermal energy within any material, solid, liquid or gas, but "internal" radiation also plays a part in such transfers.  Hence we expect radiation as a natural result of air movement and cooling.  Greenhouse gas molecules do not just sit up there collecting energy:  they radiate it out and actually collect both radiated energy and kinetic energy from other air molecules, about 98% of which are either oxygen or nitrogen molecules.  Thus it is not surprising that instruments still record a lot of radiation even at night.  After all, the atmosphere has not cooled to absolute zero and so it will still have some cooling at night as warmer air continues to rise.  The vast majority of the radiation originates in the atmosphere itself, even from the very lowest millimetre where energy is being collected through molecular collisions with the land and ocean surfaces.  The amount of radiation will however be limited by the physical rate at which the warm air rises and other factors regulating the rate of energy loss and thus the temperature gradient. 

If there were no sun, the atmosphere would still "dam" the heat flow from the core and create a base temperature at the surface.  The sun adds daily thermal energy which is mostly dissipated away each night as the temperature falls back towards the base temperature   The greater the warming, the faster will be the cooling as we can all observe when sand and rocks on a beach get hotter on a warmer day than on a cooler day, but still cool off to similar temperatures at night.   

Finally, note that the fact that upwelling radiation at the top of the atmosphere  shows missing spectral lines for carbon dioxide does not mean that the thermal energy will not escape as radiation of other wavelengths.  In fact, carbon dioxide in effect scatters the radiation it intercepts in all directions.  Hence very little continues in a straight line.  This explains why next to nothing appears from the top of the atmosphere (TOA) to be coming from any particular point on Earth.  If carbon dioxide were having any effect it would be primarily at the poles, but the Antarctic is not warming and long-term records show that neither is the Arctic.

Please continue reading ...

Second page:  Radiation & Absorption

See further information on my site earth-climate.com and here.   

*Climategate: "Explicit evidence of the manipulation of proxy records used in paleoclimate reconstructions, suppression of other viewpoints, manipulation of the IPCC process, and intimidation of journal editors were all evidence of serious breaches of ethics."   Lindzen & Douglass     Climategate 1    2

Read Dr David Evans page 2 at:  Australian Climate Science Coalition

This article explains how measurements differ from model predictions.

It's "no longer about science, but instead is all about money"

Read here about links between climate and planet orbits or solar intensity.

Case Against AGW     Prof. Claes Johnson      Possible events in the past

View comments on "Science of Doom"      Measuring backradiation    Frost

See my posts which SkS couldn't answer and deleted:  (Group 1)   (Group 2)

Decide for yourself if the trend should be curved ... Trenberth's trend

See this article and this comment for a brief summary and also my paper: Radiated Energy

Read my BOOK
"Why it's not carbon dioxide after all"
now available through Amazon
(click here)

See the latest temperature data here.

Because ocean currents circulate throughout most of the world we would expect fairly similar long-term trends almost anywhere.  Island temperatures are strongly governed by the surrounding oceans, so let's look at this historic Jan Mayen Island data, 4.3 degrees North of the Arctic Circle.  You can't miss the warmer temperatures in the 1930's. 

But carbon dioxide absorbs infra-red (IR) radiation best at polar temperatures and projections of increases up to eight (8) degrees have been made for the Arctic!   As this article shows, there is no sign of any effect due to any Greenhouse warming in the Arctic.
If you have questions email: earth-climate@outlook.com

In 1981 NASA's Dr James Hansen made a huge mistake:  he assumed that the Earth's surface acts like what physics calls a "blackbody."  But a blackbody has to be surrounded by space, or totally insulated so that it cannot lose "heat" (which should be called thermal energy) by conduction or other means to its surrounds.  The whole Earth plus atmosphere system does indeed act like a blackbody when viewed from outer space where all that can be detected is its electromagnetic (EM) radiation.  But the surface is continually transferring heat to the atmosphere by conduction and other non-radiative processes.  Besides, the surface layer of the oceans (say 1cm thin) is nearly transparent.

As this article explains, Hansen deduced (because of the above wrong assumption) that there is an unexplained 33 degree warming of the surface which he claimed must be due to the assumed atmospheric "greenhouse effect" all caused by water vapour, carbon dioxide and a few other gases which do indeed absorb the infra-red (IR) radiation coming from the surface.  But that is not a reason for warming the surface.

The assumption is made that so-called "backradiation" from a cold atmosphere is able to transfer thermal energy to a surface which is warmer than the source of the radiation. This is a physical impossibility as is proven theoretically by Prof Claes Johnson and empirically by Prof. Nasif Nahle in documents linked on the Radiation page, where there is a much more detailed explanation. 

Consider "backradiation" created by the silver reflective lining on the inside of a vacuum flask filled with coffee at, say, 97 deg.C.  The reflected radiation will not raise that 97 degree temperature at all.  Radiation which is received from a source which is cooler is rejected by being re-emitted with exactly the same frequency and energy that it had before it arrived.  Only radiation from a warmer source can lead to warming of a cooler body.  Imagine two metal plates at different temperatures placed close to each other in a vacuum.  They will each tend towards a temperature which is between the initial two temperatures.  At no stage will the cooler one cause the warmer one to get hotter still.  A mirror held above the ground at night will send back to the surface more than twice as much backradiation as all greenhouse gases combined.  According to those energy diagrams there is about a quarter as much radiation coming out of the surface, even at night, as there is coming into the surface from the Sun when it is directly overhead.  So will it make the surface warmer if reflected back?  Why would it when that coffee was not warmed by the "mirrors" on the inside of the flask?  Only direct Solar radiation warms the oceans and land surfaces.  I postulate that virtually all IR radiation which is generated in the atmosphere undergoes multiple capture and re-emission processes, including collisions with surface molecules which also re-emit it.  Eventually it finds the only escape route, namely to space.
Even if some small amount of IR radiation from a cooler part of the atmosphere does reach the surface it will not even slow the overall rate of cooling.  It can affect the rate of radiative cooling, but more than half the thermal energy that leaves the surface does so by evaporation and diffusion.  These other processes will compensate by losing energy at faster rates.  If some thermal energy is "trapped" in the atmosphere it cannot affect the temperature of the surface.  And, if the atmosphere does warm in some hot spots, it will increase its rate of radiation in order to cool back again. 

So let's start by looking at what has been happening in the real world where we will see absolutely no evidence of carbon dioxide causing any warming of the surface.  Then we will return to the issue of backradiation.

The rate of increase is falling - as would be expected if the 900 to 1,000 year cycle is approaching a maximum ...
* IPCC = International Panel on Climate Change
Do Solar Cycles hold the Key to Climate Change?
The "trend of the trend" yellow line on the above plot is an "axis" fit for what appears to be a cyclic (roughly sinusoidal) trend in the 30 year trend gradients.  This line shows that the rate of increase has reduced from about 0.06 deg.C / decade down to about 0.05 deg.C / decade.  If the long-term trend causing this is also approximately sinusoidal, then that rate of increase should decrease faster over the next 100 to 200 years, by which time it should pass through zero and start to enter negative territory.  This would indicate a maximum in the temperature trend by about the year 2200 or sooner, such maximum being 0.4 to 0.8 deg.C above the current trend.

If you are interested in climate discussion, you should be aware that the following sites censor opposing viewpoints and block comments by myself, for example:  Skeptical Science, Science of Doom, Watts Up With That, Tallbloke's Talkshop and The Air Vent.  The only site I recommend is Roy Spencer's whose data shows below: