The increase in the average temperature of Earth's near-surface air and oceans since the mid-20th century and its projected continuation.

Recognize that?   It's a definition of Global Warming.   Yes, it is obvious and clear that "the average temperature" of this planet has been increasing in the short-term.

Or as the IPCC puts it in one of their Summary for Policy Makers:

Warming of the climate system is unequivocal, as is  now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level

If it smells, tastes and looks like it's warming up, is there any reason to try and deny it?



Though why do we say in the short-term, you may ask.    Proxy measurements (such as ice cores) cover periods of time tens of thousands and hundreds of thousands of years back, and  a commonly accepted belief is that the planet itself is some four and a half billion years old.     Geologically speaking, two hundred (or even ten thousand) years is indeed a short period of time.   Even more so, when you consider a number of things, we really aren't discussing anything but a 200 to 300 year period of time, and compared to what came before it, that is nothing..

Now as everyone knows, you can't have anywhere near a proper discussion of something that is largely a scientific matter without graphs and charts and the like.  So we'll have to include some here, as we no doubt will very soon.   Nothing too extensive though.

The "average" temperature of the Earth is about 14 degrees Celsius, and the warming of near surface air and water is expressed as an anomaly.   One way to put it is that the samples are compared to a base period of some 30 years, a climatology..   In this case, we are using 1971-2000 as the base period.    (Most if not all of that is explained in the two links above, as well.)

There are many ways to express the results.  Here is the anomaly added to the "Earth average" of 14 °C and shown on an equal scale of ± 0.8 °C   The graph looks much the same without being overlaid, but this may help put it in a more obvious perspective.    

Global average temperature 1900-2007

One would imagine such a thing has a cause.  Yes, certainly there have been many periods in the past where that variation is as nothing, true.   The Vostok Ice Cores, for example, show multiple variations of more than -8 to +2 °C over  400,000 plus years.    The difference though is that this isn't the past; it's now.  This isn't ice cores either, it's direct samples of the air and water.

Often carbon dioxide levels as representative of the long-lived greenhouse gases (as opposed to the highly variable water vapor, and the non-gas clouds) as used to demonstrate a likely causal link of sorts.  Something to temperature.  There's the addition that we know we are adding carbon to the atmosphere by utilizing biomass; burning "fossil fuels,"  building factories, clearing forests and grasslands, and the like.

The ice cores don't show a period in the past where carbon dioxide hasn't been in the 200 to 280 parts per million by volume range.  Still,  those are the proxies of the past once again.   The direct recent measures of the atmospheric levels of carbon dioxide as measured at Mauna Loa tell a different story of what's going on, just  as the temperature anomaly did.

Atmospheric CO2 1900-2007

Yet even without this seeming correlation between those two, and regardless of how well any causal effect can be shown or not?  The issue here is that we are talking about now.     We are seeing things happening.    We know that greenhouse gases are responsible for the greenhouse effect.  We know that humans create greenhouse gases (and land-use changes) through their actions.

The fact is that there has never been a period of time we know of where anywhere near the number of humans or human activities has existed.     Since the 1750s especially, but to compare to the above two graphs, we'll use the same time period.

Number of humans in billions, 1900-2007

Obviously, some might claim that carbon dioxide causes humans, or that a large growing concentration of a gas that absorbs and emits infrared radiation in the 4.25 and 15 µm ranges has nothing to do with temperatures.    Unimportant.    Without humans, none of the rest exists, so such trifling bickering matters naught.

Besides all that, there's more than just charts of temperatures, atmospheric gas concentrations or population to consider.      Take for example, much like our climatology,  some 30 years of one of the things happening to the surface of the planet.  

Decrease of rural land 1975-2005

There are many ways to display and discuss the information available, and many ways to attempt to show causation and direction.  There are matters of magnitude and impact to consider.    One thing is certain however.    Humans are changing their environment through their actions.   It also appears that short of ceasing the use of technology and fossil fuels, or short of finding alternatives to them, that such things are going to continue and accelerate as more of the plant grows economically.     

The time is over for arguing about what is, and the time has come to decide what to do about it.



More?    You can see what the future holds or  read up on energy issues and the like.