In the overworked sketchbook page below I have shown several (of many) examples of how a variable such as mean annual surface temperature of the Earth might change over time (years, decades, centuries).
As we continue to struggle with the science and the impacts of climate change, it is important to understand the commentary presented by the various factions in the debate.
The fact that people are debating the science of global change is of concern, especially for a culture describing itself as enlightened.
Perhaps the variable nature of the change itself confuses those desiring consistent and smooth trends from year-to year. For matters of climate, tens and hundreds of years of data eventually provide the definitive smooth trend. Now we experience normal variability with an upward trend, somewhat like that depicted in Example E below.
What many climatologists and ecologists fear is a combination of Examples D and E. This is an increasing trend with normal variability that passes a "tipping point" and then the Earth system resets at a higher average temperature.
When we consider just the five climate feedback loops described in recent posts on this website, it almost seems inevitable that we will cross thresholds to novel conditions (for us who are used to the "old normal").
Whether or not we move to a new "stable state" or continue the upward trend of increasing temperatures depends on the actions we take now to reduce (eliminate) carbon emissions and re-establish global carbon sinks (forests, grasslands, and fertile soils).
This sketchbook page helps me visualize the concept of trends. When trends appear with adequate data, their extrapolations into the future serve much as simple computer models--but without a computer. Both help us see possibilities for the future without having to go there immediately. These are predictive because, as the saying goes, 'unless we change our direction, we are likely to end up where we are headed.'