Key Concepts: The systems of the Earth (both living and non-living) are subject to changes on many different spatial and time scales. Among these changes are shifts in both regional and global climates. On the scale of the lives of individual people and our societies these changes can profoundly affect the quality of our life. In order to understand these changes we will need a scientific understanding of how the world operates.

LEARNING OUTCOMES: By the end of the semester, every student should be able to:

Global Change: Various Scales
The world changes. And it does so in many different ways, and on many different scale of space and time.

The world, and our experience of it, varies considerably depending of the scale of our vision. As educated people we know that the objects of the world (including ourselves and loved ones) are made up of atoms, and that chemical reactions invovle the interactions of these atoms, even though we don't perceive this realm directly. Furthermore we are aware of the Earth as a globe, and the wide varieties of environments around the planet. But we live and directly experience the realm in between: our surroundings, our neighborhoods, and the places we visit. A personal worldview that incorporates the atomic and the planetary levels are simply not part of most people's lives. But during this program we hope to help expand your consciousness to keep this broader spatial scale in mind.

In terms our own personal temporal experience, we see changes such as:

Also, when the geological sciences were first developed in the late 1600s onward, it became apparent that the Earth has gone through tremendous changes of landscape, local and global environment, ecosystems, and so forth. We now know these changes to take place on the scales of 10s or 100s of thousands of years, or millions of years, or even longer.

We will definite touch upon the "annual and smaller" time scale and the "deep time" time scale (greater than 10s of millennia) during the course of the program. But the vast majority of the class will be spent on a meso-scale (intermediate scale): one of years to decades to centuries. But we have to consider: what is changing when we talk about global change? One of the main concerns, of course, is global warming (or more precisely, climate change).

What is "Climate"?
We'll revisit this issue in more detail later on. However, for the purposes for the start of the course, we'll use Mathez's short definition: Climate is the average weather for a particular region over some time. That region may be as small as a county or as big as the whole planet (global climate). Climate therefore includes weather but also variations in weather over time. Some researchers specify the amount of time represented for the averaging (30 years is a commonly used numbers), but there is no hard and fast rule.

A folksy way of saying this is "Climate is what you expect, weather is what you get."

Climate change is, therefore, changes in the statistics of weather for a particular region over some time. Nothing in this definition requires climate change to be anthropogenic (human made), nor tied into changes in greenhouse gasses, nor be especially about warming per se. (As we will see, however, recent climate change is all three!)

Here is a video of the distribution of summer temperatures relative to a 1951-1980 mean of Northern Hemisphere summer months (June-July-August) (From the Goddard Institute of Space Studies, NASA):

Here is another look: the Berkeley Earth Surface Temperature (BEST) Project's reconstruction of changing temperatures over the course of the instrumental record (that is, the period of time when there are thermometers and such to actualy take the temperature of the environment):

Or, we can look at the GISS temperature data, plotted for each month, for planetary temperatures:

So why should we care if temperatures change? Of concern to human affairs are three main consequences of climate change, which can perturb human affairs directly or via their effects on other parts of global systems. These three consequences of climate change are:

As the course proceeds, we will see how each of these is affected by changes in the drivers of climate change, and how changes in these affect human society and technology, in far more detail. But to get us going, let's consider that changes in these factors (individually or collectively) can impact:

We will spend much of the second semester dealing with how climate is generated, and how human activities can impact this. However, here is the briefest of overviews of how human technology modifies global climates: aka, the greenhouse effect:

In the second and third semester we'll see how some historical societies suffered under smaller-scale natural climate changes, and how our own society will have to deal with comparable or more extreme difficulties in years and decades to come. Here is a taste of what is in store:

NOAA's Geophysical Fluid Dynamics Laboratory model for future 21st Century warming:

And their models for changes in precipitation distribution and future droughts:

So how are we able to model future events, or even understand the world around us? How do we know anything at all? That is the focus of the next several weeks: understanding the Nature of Science!