Here is what goes on in the atmosphere when CO2 meets IR in its frequencies.
The simple truth is that CO2 has only been shown to absorb energy as IR and in the same moment release it because CO2 cannot hold additional energy. The fate of the released energy is not quantified in terms of an open atmosphere.
What happens is that the surface absorbs solar energy and emits IR. Land stores energy only as long as air temperature suppresses release. The atmosphere is a weak reservoir of energy, it loses T rapidly, counted in hours in the absence of solar input. As air T falls the land cools rapidly, e.g. day to night and summer to winter for land affected by the height of the Sun above the horizon and not at a fairly constant high humidity level, i.e. other than the Tropics. Oceans being less opaque to incoming radiation store energy more deeply and so for longer. This is clearly shown by coastal regions cooling more slowly than inland areas.
The surface emits energy. Focusing on surface IR radiation, for a given amount of emitted energy there is a constant exchange between molecules and between energy forms. A collision with a CO2 molecule, provided the molecule doesn't pass on the energy by contact will cause the CO2 to emit radiation in its frequency range that will be predominantly absorbed by WV (whose ranges of absorption overlap CO2's), residually by another CO2 molecule. Adding more CO2 will increase the likelihood of radiation being created but as this travels at the speed of light the reaction and reabsorption is momentary, the moment increasing in duration as we follow the energy trail upwards. Sideways emitted radiation is irrelevant to the argument. Downward radiation meets increasing density (in population of atoms per m3, ppm is misleading) and the radiation emitted has an increasingly shorter lifespan. That slightly less CO2 emitted IR is emitted down than up is a factor due to curvature of the surface and atmosphere that biases the flow upwards. So we can make an observation, number 1.
Adding more CO2 increases the likelihood of IR production in the air. Because the bias is upwards, increased radiation downwards is over compensated by upwards radiation.
So we have X amount of energy as IR emitted by the surface, CO2 passes most of it (near 100%) to kinetic or potential by collision within 100mtrs and that contributes to accelerating convective and conductive upward flow, accelerating those cooling mediums whereas in IR form the IR would otherwise be lost to space. Downward emitted radiation e.g. from clouds, meets a similar fate due to the CO2 population, increasingly contributing to other means of upward movement of heat energy with distance travelled downwards. That gives the second observation.
Adding more CO2 increases the likelihood of IR energy being converted to kinetic and potential energy that must enhance convective and conductive upward transfer of energy.
At the top of the troposphere the predominant method of energy transfer across the tropopause boundary (temperature inversion) is by radiation. With a higher population of radiation producing molecules, a higher proportion of energy is converted and is available for transfer. The radiation that is not absorbed and remitted upwards is converted to the other energy forms and conveyed back upwards. Even were the fraction radiated downward not less than 50% diminishing downward penetration due to increasing atmos. density guarantees a greater proportion of energy is radiated up with an increasing population of CO2. hence a third observation.
At the tropopause an increasing population of CO2 leads to a higher rate of collision-conduction stimulated IR emission by CO2 and so increases upwards transmission whose volume exceeds downwards transmission as discussed above.
Why did upward radiation at the TOA in CO2 IR frequencies fall before increasing? When talking of the CO2 IR frequencies, gross the amount is around 8% of the spectrum. Where WV is present in sufficient volume, it is responsible for absorbing much of the IR in the CO2 frequencies where there is overlap. So WV is mostly responsible for blocking CO2's OLR (outgoing longwave rad.). Since the top of the troposphere emissions have shown an increase in CO2 IR upward emissions, this can be considered evidence that increasing emissions to space are occurring due to the increasing productivity of the higher density of CO2 that in turn is caused by a reduction in the IR taken by WV. The upper atmosphere including the stratosphere dried (Sue Solomon) as the stratosphere cooled due to successive eruptions. Aerosol injection by eruptions provided the base for condensation and crystal formation. The reducing TSI seen this century has meant less solar UV energy for ozone to convert to heat so recovery has been further slowed as ozone forms more slowly in cooler temperatures. A cooling stratosphere causes a slowing of air currents, a less turbulent tropopause and easier passage for the crystal precipitation downwards. Lower levels of UV reaching the oceans both due to ozone recovery and reducing solar emission has reduced evaporation, the main supply source for the upper atmos. WV reservoir. The next observation is thus arrived at.
WV stores IR energy in the frequencies shared with CO2, preferentially where there is an overwhelming WV volume, and radiates at frequencies outside CO2 ranges. Reducing humidity leaves absorption of IR in the overlap absorption ranges increasingly to CO2. CO2 does not store energy and radiates IR in its frequencies.
CO2 warming influence in the stratosphere is not considered relevant due to the decreasing with height population per m3 and the air temperature rising with height from the inversion at the tropopause. CO2's IR frequencies are so low in energy that they cannot increase the temperature where molecules are at a higher energy level. It is relevant when considering upward radiation emission, in a drying stratosphere there are less molecules that trap CO2 IR frequencies so more energy is radiated to space.
The diagram prepared by Cimate4you can be approximately related to year by comparing CO2 values. [1965 on the left, 2010 on the right. 360 ppm equates to 1995 according to MLO]
OLR data from NOAA 10.5-12.5 µm - 179oE and 179oW and 90oN and 90oS June 1974 to July 2010.
Source and full specs here.
The final observation.
In the presence of WV the influence of CO2 additions in delaying energy movement upwards is at least insignificant to a high order and very likely accelerates it insignificantly.
In the presence of molecules at a higher energy level than that produced by CO2 IR frequencies, CO2 cannot increase those energy levels by IR absorption.
Due to the upward bias caused by curvature of the planet surface and atmos. and due to decreasing density with height, additions to the CO2 reservoir accelerate the upward flow of energy.
In the absence of WV, due to CO2's inability to store energy, additions to the CO2 reservoir further accelerate the upward movement of energy.
CO2 does not manufacture energy and so cannot increase the energy level, i.e. increase the temperature.
CO2 fails to enhance warming at any volume seen and very likely at any achievable level.
With reducing energy input CO2 enhances cooling.
Separately, the climate is cooling and there is evidence.
Reducing evaporation leads to lower humidity in the upper atmos. This allows higher levels of radiation in WV's frequencies resulting from molecule collisions to be emitted to space. This is offset by a corresponding reduction in cloud formation causing a lower level of solar radiation to be reflected by albedo but that is compromised by less upward IR radiation being absorbed by the clouds and increasing ice albedo at the surface. The reduction in energy reaching the surface due to rising ozone volume and reducing solar activity further enhances the cooling effect of increasing IR radiation.
The climate is varied by surface IR production due to solar emissions that are moderated by ozone and albedo, WV production that determines the detention period of IR, cloud and upper atmos. ice crystal formation (volume) that are a significant determinant of albedo, and political interference in aerosol and sulphate emission by human activity. In a warming atmosphere CO2 is irrelevant. In a cooling atmosphere CO2 accelerates cooling, albeit insignificantly.
Image source and additional info as for the other image.
Solar irradiance and sunspot number
Also see Ozone and Rapid Climate Variation