You said “Let us further assume that the change is a random variable with a mean of 0”. It isn’t a random variable and doesn’t have a mean of zero.
Over short-time periods then the climate can be considered to be random, there are a multitude of variables that influence the climates many of which induce some amount of warming or cooling.
Across millennia the amount of change can vary from as little as ~0.0000005°C per year to as much as ~0.0006°C per year. Such changes are consequent to the way Earth and the Solar System moves in space and our relationship with the Sun. It’s these factors that determine the prevailing climate on Earth. These factors are not random, they follow defined paths that repeat at frequencies of between 22,000 and 120,000,000 years.
On timescales of perhaps a few centuries, the magnitude of warming or cooling can be greater, by as much as 0.001°C per year. Again, this isn’t random, it’s trends that last for centuries.
On a decadal timescale the change can be greater still with natural variations of as much as 0.01°C per year. Such changes are tied to cyclical and oscillatory influences and are not random.
Where there is a greater degree of randomness concerns variations on a scale of a few years or less. One example would be the El Nino Southern Oscillation. The duration of any episode is variable and largely unpredictable, so too are the phase changes and the lengths of each phase.
Over a period of a few years, ENSO and other variables can influence weather in an unpredictable manner. That’s why climates are based on long-term trends. Within any baseline period, and any period under test, there will be enough random variables to more or less cancel each other out.
It would be possible to go back through historical climates and identify periods when the mean, of pretty much every variable, was zero; but you’d have to take the variables one at a time.
Within the climates there are variables nested within variables within variables, probably down to about 20 levels. It’s possible to define a period when variable X had a mean outcome of zero but the variables around it would be all over the place.
The foremost variable would be the one that would define the longest term trend but within this there would be times then the net effect of other variables more than compensated for the first trend and for a period the climates would go against the overall trend.
For example, within the galactic cycle Earth is cooling (the longest one), within the eccentric cycle it’s cooling (the most dominant on human timescales), within the SSN signal it’s cooling (the strongest century-wide one), within the PDO signal it’s cooling (the strongest decadal one), within the ONI signal it’s neutral (the strongest annual one). Despite the fact that all these significant signals bar one, are cooling, the planet is still warming, albeit much slower than 20 or 30 years ago.
If it were a random walk there would be no clear trends, and this just isn’t the case.
There are just too many unknown variables. For example just recently man has discovered masses of streams of Methane being released on the ocean bottom. If Methane is a GHG then how could you compute that into your calculations even if the total effects were known? Last year scientists were discovering a new subocean volcano every day. These are just a very few of the problems in order to get an accurate prediction.
Also the Sun in the climate models is treated as a constant. That is wrong! It must be treated as a variable and who can look to the future and see what the sun will do?
A random walk has a Gaussian distribution to it's changes but as it is ongoing, any sample size of data would be insufficient for a Gaussian analysis hence a Cauchy or T-student distribution would be required for analysis which means the claims by deniers that there is no change is invalid. It also means the claims there is change are also uncertain as there is no mean or standard deviation to a Cauchy distribution though there is a median.
The thing is, the variables seem random, because we're not fully aware of the underlying mechanisms, but they are based on real physical processes.
There are probably, at a minimum, *thousands* of variables that affect temperatures. Some of them are cyclic, some of them are more or less random, and some of them--like anthropogenic CO2--are steady or semi-steady increases or decreases.
But they are all representations of or modifications of quantifiable inputs (like solar energy) and outputs (like the energy Earth radiates into space). They are not "truly" random.
You can think of it a tiny bit like a deck of cards. No matter how much you shuffle the deck, the card you draw *will* be one of the 52 cards in the deck. No amount of randomizing will create, say, a 0 of hearts, or an emperor of spades.
Oh no. You forgot that it is a devious 30 year plot of nearly the entire scientific community worldwide to raise taxes and establish worldwide dominion for the Illuminati Conspiracy. The takeover is already underway
My observation is that there are more variables than known. This is why every prediction to date has failed. Events must happen first, then the explanatory fiction is created around a pseudo scientific shell to explain what was observed.
yes global warming is random walk because it is increasing day by day due to human activities.people throw wastage carelessly and harmful smoke from different factories are producing randomly which pollute the environment.
no the Earth has long and short cycles
Lets assume that the global temperature is dependent upon the previous global temperature with a change. Let us further assume that the change is a random variable with a mean of 0.
This would mean that the global temeprature is a "random walk". The problem with this assumption is that random walks tend to go off to positive or negative infinity. Since clearly the global temperature does not, there must be a mechanism or feedback that resists change and tends to bring the temps back to equilibrium.
To me, this would mean that the negative feedbacks inherent in the system must outweigh the positives. Does this not fly in the face of the large positive feedbacks assumed with the current IPCC predictions?
