Many people in the media (and elsewhere) use the terms "climate change" and "global warming" interchangeably, as if they were the same thing. But there are differences between the meanings of the two terms. Getting a better handle on the definitions of and differences between "global warming" and "climate change" will help us understand why the threat caused by continued warming of the planet is so serious.
Global Warming — An overall warming of the planet, based on average temperature over the entire surface.
Climate Change — Changes in regional climate characteristics, including temperature, humidity, rainfall, wind, and severe weather events.
Let's explore the differences between these two concepts in more detail.
Planet Earth's current warming trend is based largely on natural warming and cooling cycles that have been happening for eons; as well as human-caused additions to greenhouse gases, which are boosting the atmosphere's ability to trap heat in the biosphere. Minor factors like an overall increase in the sun's solar intensity play a smaller role.
While greenhouse gases are an essential component of a livable planet—they're what keep Earth from being a lifeless ball of ice—humans are causing greenhouse gas levels to increase so quickly that it's causing the average global temperature to rise much faster than it would naturally.
This warming is predicted to lead to a variety of negative effects, including:
- Melting (and possible disappearance) of glaciers and mountain snow caps that feed the world's rivers and supply a large portion of the fresh water used for drinking and irrigation.
- A rise in sea levels due to the melting of the land-based ice sheets in Greenland and Antarctica, with many islands and coastal areas ending up more exposed to storm damage or even underwater.
Increasingly costly "bad weather" events such as heat waves, droughts, floods, and severe storms.
- Lowered agricultural productivity due to less favorable weather conditions, less available irrigation water, increased heat stress to plants, and an increase in pest activity due to warmer temperatures.
- Increases in vector-borne infectious diseases like malaria and Lyme Disease.
- Large numbers of extinctions of higher-level species due to their inability to adapt to rapidly changing climate and habitat conditions.
The first two of these effects are mostly related to increasing average temperatures. Items 3-6 are related to heat too, but also playing a role are non-temperature factors—i.e. "climate-change factors."
Climate change is about much more than how warm or cool our temperatures are. Whereas "global warming" refers to increasing global temperatures, "climate
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change" refers to regional conditions. Climate is defined by a number of factors, including:
- Average regional temperature as well as day/night temperature patterns and seasonal temperature patterns.
- Precipitation (average amounts and seasonal patterns).
- Average amount of sunshine and level of cloudiness.
- Air pressure and winds.
- Storm events (type, average number per year, and seasonal patterns).
To a great extent, this is what we think of as "weather." Indeed, weather patterns are predicted to change in response to global warming:
- some areas will become drier, some will become wetter;
- many areas will experience an increase in severe weather events like killer heat waves, hurricanes, flood-level rains, and hail storms.
It's tempting to think that all of these changes to the world's climate regions will average out over time and geography and things will be fine. In fact, colder climates like Canada may even see improved agricultural yields as their seasonal temperatures rise. But overall, humanity has made a huge investment in "things as they are now, where they are now." Gone are the days of millennia ago when an unfavorable change in climate might cause a village to pack up their relatively few belongings and move to a better area. We have massive societal and industrial infrastructure in place, and it cannot be easily moved. Climate-change effects will generally not be geographically escapable in the timeframe over which they happen, at least not for the majority of humans and species.
Beyond mere "weather," we can also think of a region's climate as a place in which things live—a la, "a hospitable climate." Therein lies the real danger of global warming—climate change will affect the success or failure of how plants and animals live in a given geographic area, including food crops.
We think of the Central Valley of California as a lush, agriculturally productive landscape, but central California's climate is actually quite dry. Without intensive use of irrigation, the land would not produce the volume or variety of food it does now. So, what if increasing temperatures cause less snow pack to accumulate in the mountains each year, leading to lower river flows and less water available for irrigation in California's agricultural areas? What if changes in rainfall patterns make central California's climate even drier? How much would crop output fall?
This is just one example of how global warming could lead to a regional climate change that would cause a big difference in local economics and the national food supply.
Even though the main threat right now is warming planetary temperatures, climate change can also mean global cooling. The last Ice Age was part of a globally cool period and it featured some rather severe "climate change" characteristics.
It's worth remembering that global warming is based on an increasing average global temperature. Some parts of the planet (such as the Arctic) are getting warmer much faster than other areas. It's even possible that some regions could actually experience regional cooling at the same time the planet as a whole is experiencing global warming. Here's how.
The "thermohaline circulation" in the world's oceans is part of the planet's temperature regulation system. It can warm or cool regional climates to make their average temperatures different that they would be normally based on their latitude.
The most notable example of this is how the Gulf Stream brings warm water up from the tropics to make Europe much warmer than it would be naturally. This part of the thermohaline circulation is dependent on regular additions of fresh water from melting Arctic ice (which is replaced every year through additional snowfall). If the flow of fresh Arctic water decreases enough, it could slow or even stop the thermohaline circulation, leading to cooler temperatures in Europe—even at the same time other areas are experiencing severe temperature increases.
Global Warming vs. The Next Ice Age
Those who are skeptical about the threat posed by global warming often point to the fact that a few decades ago, some scientists were warning us that a new ice age could wipe us all out. After all, during the last Ice Age—which ended 10,000 years ago or so—much of North America was covered with an impenetrable sheet of ice. A repeat of that would indeed be big trouble.
Because of scientists' previous warnings that a new Ice Age might be in our future, global warming skeptics sometimes say that scientists can't make up their mind—first it's global cooling, then it's global warming. But let's remember three things:
(1) Back in the 1970s, at the same time a few scientists were warning of a possible new Ice Age, other scientists were already warning about the emerging evidence of global warming.
(2) The scientific community is now overwhelmingly in agreement that there is a threat from global warming and that there is no threat of another Ice Age, at least not in the timeframe that counts.
(3) The amount of temperature increase predicted from now to the end of the century is roughly the same as the temperature difference between now and the last Ice Age. (Yes, really!) It would be foolish to think that an equivalent but opposite move in temperature might be a good thing.
There are important differences between global warming and climate change, but the two are closely intertwined in determining the climate futures for the regions where we live. Predictions of regional impacts are beginning to emerge from climate models. There are regions that will get some benefits, but most of the predicted effects around the world are bad—bad enough that we need to quickly start fixing our greenhouse gas emissions.
There are solutions, but most leaders today are offering only low-impact solutions that will not truly solve the problem. We need to be talking about how to cut greenhouse gas emissions by 50%-80% over the next few decades, not dithering over minimalist efforts like how to get back to 1990 levels by the year 2020.
Some leaders just offer excuses about why no action is possible, citing "the economy" as a reason to continue ignoring the problem. But a report from the British government about the economic damage that will be caused by inaction on climate change makes it clear that continued delay is unwise, even from an economic standpoint.
Many of the actions necessary to solve the global warming problem must be attacked at the national and international levels. But in the US, states and cities are thus far in the lead on implementing solutions. In the end, total success will have to be built on our actions as individuals (regardless of country), from energy conservation to vehicle choices to what we demand of our leaders. You too can be part of these global warming solutions!