If the global warming from 1865 to 1940 is deemed NATURAL, why think the warming from 1940 to present isn't?

There is no mystery, both periods were natural and well within natural variations.

There is still so far no empirical evidence that points to CO2.

Because back then people didn't even care about the environment. I'm sure the industrial period screwed up the earth badly but they didn't give 2 cents about it. It's not until recent that people became conscious of what the industry is doing; that is why global warming from 1865 to 1940 was deemed natural.

You're always going to have extreme fluctuations in ground-based measurements, but the determining factor really depends on how accurate the plot points are to actual temperature. We all know that the Earth is full of "blobs" of temperature that can move swiftly around the globe, especially close to the surface, This is where the "temperature mixing" begins. Having measuring stations at 1,000 mile intervals will never capture TRUE temperatures. The graph that you presented still has a + or - 0.3C accuracy factor as to what the ACTUAL temperature of the surface REALLY is and the earlier measurements have an even wider margin of error as to the TRUE temperature of the Planet's surface.

BOTTOM LINE :

Temperature readings from the past still have a lot of variables to consider as to their accuracy. Climate Science would be better served with "snapshots" of temperature from around the World and at the same time to get a better view of where surface temperatures stand at this point in time. It would require 4 separate 24 hour days ("snapshots" every hour - 10,000 measurements taken at one time) and about 10,000 people to do this. I believe the question of ACTUAL surface temperature could be solved this way.

Additionally :

Knowing that many places in the World can go through temperature changes of up to 15C to 20C in a matter of minutes (Chinooks for example) just shows how inconsistent the past, current, and random temperature readings are. Using satellite "feeds" to instantaneously measure temps around the World 96 times a year (960,000 measurements a year) could be very easily verified. Barometers and relative humidity measurements could also be entangled into this system, but I'm afraid that "politics" will always infiltrate any means simply because of the various interpretations of what the science means (basic human bickering). It's unavoidable, but a running history would be much more reliable than having to keep changing past data through a $500 billion computer as we have been doing for the past few decades.

Interesting question ...

What various scientists around the world have tried to do for decades is build up a picture of what the climate was like in the past. In the past 100 years or so, we have pretty accurate temperature records from various locations around the world. We can also use things like analysis of tree rings, changes in tree line positions, sediment on the ocean floor, and the animal and plant species that were present to try to infer what the climate was like in the more distant past. We can look at air bubbles trapped in ice to build up a picture of the atmospheric concentration of various gases. So the point is you have lots of scientists in a variety of different fields who attempt to build up a picture of the climate in the past. We call this 'proxy climate data' because we aren't directly measuring the climate (we can't travel back in time with modern equipment!).

What some scientists, or climatologists, study is the processes that influence our climate. Those processes are based on physics, chemistry and biology - the sun pumps out a certain amount of energy, the earth is a certain distance from the sun, that means we get a certain amount of energy per second per square metre. This energy interacts with an atmosphere we can mathematically model with gases we can study the properties of, and also interacts with the ground and oceans we can study in terms of their thermal properties. We can look at the concentrations of the gases in our atmosphere, relate that to the ocean area we think there was based on geology, and the amount of plant life there was based on soil depths, etc.

What these climate scientists have been doing for the past century or so is developing mathematical rules that govern the climate of our planet. In all areas of science, when you develop mathematical laws that you test against observation you can call it a 'model'. Newton's law of gravitation is a 'model' of gravitational force that you can apply. Einstein's special relativity is a 'model' that you can apply to fast moving objects. And similarly, we have 'models' that you can apply to climate.

So what the climate scientists have done is taken the models they developed, and used them to simulate what the climate of our planet should have been like in the past based on those models. They then take the proxy data for climate and the more recent actual measurements performed using apparatus and compare the model results to the evidence we have for what the climate was actually like. When they do that they find that the models do an excellent job of matching the data! What you have is what science is all about - building models of reality that, when applied, match observational and experimental data.

Now the problem is that the models always contain some uncertainties. For example, you might run your model and compare it to proxy data, and find that the temperature over some century was higher in the proxy data than your model suggests. This is good for science because it helps to direct research. It might be that the model underestimated the output of the sun during that century. But other scientists studying proxy data might then find evidence supporting the conclusion that the output of the sun was higher. This new evidence can be folded into the model. So you see, as in all areas of science, the model and observation go hand-in-hand. New observational / experimental data means tweaking the model, areas where the model doesn't match observation suggest aspects that need to be investigated further.

But the beauty of a model is you can then push the parameters out. What would happen if in your model, you decided that 2000 years ago, the CO2 concentration was doubled and the solar output was increased? You can then test this scenario against the proxy data. At some point you'll find that when you push the parameters too far one way or the other, you no longer have a model that matches the proxy data. In other words, you can define limits above which your model no longer matches the experimental / observational data.

The point is that this is exactly what climatologists have done. They have models that have certain boundary conditions and upper limits for various parameters that match proxy data for climate. What they found was that the models that work perfectly well for this proxy data suddenly fail to match the observational data taken since the 1970s. The scientific question is 'why do multiple models of the climate, with parameter values that have been tweaked and sit within boundary conditions that work perfectly well for proxy data for thousands of years suddenly fail at a specific moment in time?'

When they include the CO2 and other gases that we've been emitting for the past 100+ years, they get their answer. In the early part of this century, natural factors swamped the impact of those gases. As we increased the concentration in record time (CO2 levels haven't been at the current level, or risen as fast, at any point in the past 800,000 years) our additional CO2 forced the temperature of our planet to rise. And when you factor in the amount of CO2 we've pumped into the atmosphere, all of a sudden the models come back into line with observation.

Since the first models in the 1980s, we've amassed a huge amount of evidence that a) the rise in CO2 levels we've observed since the 1900s is not natural and is predominantly due to our activities, and b) the planet is warming at a rate that is, in terms of the physics, consistent with that observation.

On come on they are trying to convince people they are all going to die if they don't give up their present life style and let them (the greenie, leftist, socialist) dictate how they live. It is a con job. Plain and simple. They aren't even hiding it. Some of them are even saying it plain out to everyone's face.

How much plainer does it have to be. What do they have to do? Run 24 hour a day telethons announcing it.

Is there any reason for choosing those time periods? Just curious.

Anyway; I wouldn't say that there was no man made warming between 1865 and 1940, just that what there was, was much less than today.

Looking at the two periods, we have around 0.1C for the earlier, around 0.35C for the later. Is that really the same amount of warming?

http://woodfortrees.org/plot/hadcrut3gl/from:1865/...

What is your evidence that 1865 to 1840 was DEEMED NATURAL?

You said this was global warming - natural?

You must be using the old data, Maxx. James "climate chiropractor" Hansen "adjusted" surface temperature data to make the first part of the 20th century much cooler and the very end much warmer. The adjusted data also shows a much stronger warming trend over the last 20 years of the 20th century.

If the data doesn't fit your hypothesis, change the data.

No. Global warming has been influenced by human activity since the start of the Industrial Revolutions, about 1850.

Because from 1865 to 1940, the Sun was increasing its radiation output.

After 1970 or so, the Sun has been putting out LESS radiation.

And of course, there was much more CO2 during the latter period.

Professor Lindzen posed the man-made v natural warming question about the graphs below.

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