The psychology underlying people’s behaviour is as fascinating as the things they do. “Change blindness” is a case in point. Psychologists describe it as the inability of people to notice anomalies, differences and the unusual in their surroundings. The obvious, it seems, is not always obvious. Two classical examples of change blindness, both conducted as experiments at American universities, serve as illustrations.

The first is known as the “invisible gorilla”. In the middle of a basketball game, a gorilla wanders onto the court — actually, it’s a man dressed in a gorilla suit but he looks, moves and acts like a gorilla. He lumbers around the court, mixes with the players and then exits through a side door. Half the spectators, when questioned afterward, failed to notice the gorilla. They were apparently so intent on the game that they didn’t register such a strange anomaly.

In a second experiment, a stranger on a university campus stopped individual people to ask for directions. In the middle of the resulting conversation, two men carrying a large door passed between the stranger and the person offering directions. During that brief moment, the stranger was replaced by a second stranger, someone of different height, build and clothing. Half the people in the experiment failed to notice that the stranger they had been talking to had been replaced by a second stranger.

Change blindness occurs, psychologists suggest, “because it is not possible to perceive and remember all of the details” that surround us (New Scientist, Feb. 19/11). It also occurs because we stitch together events to fit the reality we expect, keeping the familiar ones that are comfortable while leaving out the others. And, additionally, we sometimes fail to even register sensory evidence that is totally foreign to our sense of reality. Change blindness smooths over events and circumstances to make them compatible with our sense of normal.

This psychological dynamic becomes relevant when applied to environmental matters. And the implications are not reassuring. For example, we seem to have an inherent inclination to overlook or rationalize as normal the weather abnormalities that arise from global warming. If this strategy doesn’t serve to diminish the significance of an extreme weather event in our minds, we excuse it by extending the range of normality — a once-in-a-century event occurring once every ten years is deemed normal. This is a psychological mechanism we use to excuse the significance of exceptional floods, rains, snowfalls, winds, droughts and hot spells. We quickly adopt new extremes into a new normal so that the exception goes unnoticed. Shifting the criteria for normal is one way of activating change blindness.

Because most people now live in the comfort of urbanization, surrounded by human creations and separated from the natural world, the unusual absence of a species of bird, animal or butterfly goes unnoticed. But even when noticed, the absence quickly becomes a new normal, whether this be silence, darkness, missing fish or old-growth forests. Accounts of old timers describing huge salmon runs become a fiction that fails to illustrate the dramatic deterioration that has taken place in a mere lifetime. An environmentally diminished present quickly becomes the new and accepted normal.

Scientific studies that underscore the significance of ecological damage are commonly discredited by change blindness. The public’s impulse is to construe disturbing scientific evidence as opinion because its threatening facts don’t fit into the established system of normalcy. In essence, we have difficulty accepting information that conflicts with our paradigm of understanding — belief takes precedence over evidence. As Marshall McLuhan noted in one of his famous adages, “I wouldn’t have believed it if I hadn’t seen it” is replaced with ”I wouldn’t have seen it if I hadn’t believed it.”

Which raises a more sinister issue. This is the impulse to control evidence in order to control public opinion — deliberately using change blindness for calculated purposes. Scientists in the employ of Canada’s present federal government have repeatedly and increasingly voiced concerns about being censured. Even though these scientists may profess political neutrality, the reality is that all the evidence they collect has unavoidable policy implications — no information is politically neutral. A public without evidence of unprecedented environmental shifts doesn’t register a problem.

Thus, change blindness keeps us from anticipating the future — or, more accurately, the future we anticipate is based on limited experience. Curtail experience and our ability to adapt to climate change or a melting Arctic is handicapped. If oil spills are not part of our personal history, then the real ramifications of oil tankers emptying Northern Gateway’s Alberta crude into pristine West Coast waters is unlikely to register. If wild salmon have always been a part of British Columbia’s ecology, then the actual devastation that could be caused by destructive diseases and parasites emanating from open net-pen salmon farms is unexpected.

This is why history always surprises us. Change blindness keeps us from perceiving what is happening slowly — until the unwanted consequences cannot be avoided. We won’t notice the new stranger if we haven’t registered the first one; we can’t remove gorillas from a basketball court if the action of the game absorbs all our attention.

Unfortunately, the faster we move as a civilization — the more dense, complicated and speedy the surroundings that contain us — the less likely are we to notice what our civilization is doing, where it is going and what it is forfeiting. The energy, excitement and promise of modern civilization is, ironically, an ingenious distraction from its own failings, adroitly hiding from us what it is inflicting upon us. Indeed, this spell of obliviousness functions best in the ubiquitous, intense and unrelenting character of our age. Change blindness keeps us from noticing the changes that are carrying us into an uncertain future.

The chainsaws are still snarling weeks after the windstorm of March 12, 2012, busily cutting up the thousands of trees that blew down in forests, fields, roadsides and yards. Firewood seems to be the preferred fate for most of these once stately trees. Most of them will probably just decay on the ground where they have fallen, although some of the larger ones may become lumber. With this exception, they are all examples of feedback.

Two principal dynamics are at work in the global warming process that is changing the planet’s climate. The first is “forcing”. This is the term climatologists use to describe the initial heating effect of the gases we emit into the atmosphere. The best known of these is carbon dioxide — about 33.5 billion tonnes of it per year now come from our burning of fossil fuels. Methane, also a significant influence and about 20 times more potent than CO2, escapes from oil and natural gas wells, garbage dumps and untreated sewage. Other less known gases such as hydrofluorocarbons also contribute their influence. Another forcing process is deforestation, our deliberate removal of forests for fibre, lumber, agriculture, roads, urban sprawl, right-of-ways or any other purpose.

The dynamics of forcing are fairly clearly understood. And we can correct its damaging effect on climate simply by reducing or stopping the offending emissions. “Feedback”, however, is a more complicated problem. It is the consequence of forcing, a process that is potentially much more dangerous because it sets in motion conditions that are beyond our control once we have initiated the global warming.

As the temperature of the atmosphere rises from forcing, secondary event begin to accelerate the warming. Carbon dioxide, for example, dissolves in the ocean to form carbonic acid, and the increasing acidity impairs the growth of the phytoplankton that transform CO2 into oxygen. Higher levels of CO2, therefore, handicap the process that is absorbing and reducing the problem gas. A similar effect occurs with terrestrial plants. They, too, absorb CO2. But temperatures and levels of CO2 beyond a certain threshold begin to slow growth and impede carbon dioxide uptake. Feedback, therefore, accelerates the warming process.

Other worrisome feedbacks also occur. Melting ice and snow in polar regions expose water and land to the warming effect of sunlight. Without the reflective cover of white, the so-called albedo effect, more surface heating increases the melting which, in turn, melts more ice and snow, thus causing more heating. This is why polar regions are warming at two to four times the rate at lower latitudes.

More feedback trends are occurring in polar regions. As permafrost melts, huge amounts of methane are released. In classical feedback fashion, the escaped methane heats the atmosphere, causes more permafrost to melt and releases more methane to melt even more permafrost. Similarly, cold and pressure hold vast quantities of methyl hydrates in solid storage at the bottom of northern oceans. As these oceans warm, the hydrates effervesce, release methane and heat the atmosphere to add even more warmth to the ecosystems.

Lay critics of climate change theory often confuse forcing with feedback. In the complex subject of global climate change, one misunderstanding has been clarified for deniers by the astute reply of a climatologist who made the simple distinction between forcing and feedback. Cloud formation is known to cause warming because it reflects radiant heat back to earth — this is why clear nights are usually cooler than cloudy ones. Deniers argue that the warming process is simply caused by more clouds. Clouds, however, are the result of atmospheric humidity. And higher temperatures increase the activity of the hydrological cycle. As greenhouse gases force up temperatures, humidity increases, clouds become more prevalent, and they become feedback that accelerates the warming.

These are examples of “positive feedback” — results we don’t want. But “negative feedback” can also occur to slow the global warming process. Volcanos are the best natural example. When millions of tonnes of sulphates and particles explode into the atmosphere by a huge eruption, the gas and debris reflect sunlight back into space. The planet can cool for years or decades, sometimes by as much as 2°C — some eruptions may have shifted the climate balance enough to initiate ice ages.

We can cause the same cooling effect by adding specific pollutants to the atmosphere. Climatologists noted a sudden and inexplicable rise in global temperatures during the 1980s, a rise that couldn’t be explained by the increase in greenhouse gas emissions. The spike in temperature was caused by efforts to reduce air pollution from the world’s factories and coal-burning thermal plants. The reduction in atmospheric sulphates and soot cleaned the air and accelerated planetary heating. The same process occurred during the days immediately following the 9/11 terrorist attacks in the US. With all passenger planes grounded over North America, the skies cleared of contrails and particulates, causing a surge in regional temperatures.

But most feedback is positive, amplifying the effect of forcing. Windstorms topple trees. Downed trees can no longer sequester carbon from the atmosphere and replace it with oxygen. Decaying wood releases carbon dioxide and methane that become net contributors to the problem of global warming. So the snarl of chainsaws is more than just the simple aftermath of a windstorm.