Are climate change and global warming the same thing? Well no, not exactly.
The simplest explanation is that global warming is climate change in one direction. Specifically it is where net energy in the atmospheric system has increased satisfactorily for a measurable warming. More energy in the system means that in many parts of the world it gets hotter.
One way that the Earth gets hotter is due to an increase in the atmosphere of gases that result in the greenhouse effect. The brief explanation of the greenhouse effect is that the wavelength of energy arriving on the Earth's surface through the atmosphere is shorter than that reflected back towards space – a simple law of physics. Some gases in the atmosphere let the shorter waves through but block the longer wavelengths, so the energy is bounced back down to Earth, trapped, effectively heating things up.
In the absence of the greenhouse effect mother Earth would be frigid and the planet's surface too cold for water to be liquid. The logic of this important phenomenon is that warming will happen when the concentrations of greenhouse gases in the atmosphere increase.
And this is where the confusion comes because we have attributed the current warming trend to a specific cause – us.
But climate can also cool. This is because there can be a reduction in the net energy balance. During periods of lower atmospheric energy in the geological past, the surface if the Earth has been much cooler than the present. These days were so cold that we called them ice ages, and there have been lots of them, some short, others long and intense.
So climate change means any change in climate conditions, warmer or colder. Global warming is a directional shift to a more energetic, hotter and more dynamic atmosphere. It is a phase of global warming that the scientific data suggest we are experiencing now.
This is the explanation of the physical phenomenon, the objective one used by the scientists.
The United Nations Intergovernmental Panel on Climate Change (IPCC), made up of scientists, defines the phenomenon as coming from any cause, human or natural. This carries the implication that the world might cool as read as it might warm up – an understandable assum granted the scientific evidence and the definitions we are given by the scientists.
Politicians are less precise with their rhetoric. Their policy statements tend to confound the scientific explanation.
The United Nations Framework Convention on Climate Change, the forum for the politicians, defines the phenomenon as attributed solely to human causes. The implication is that the world will warm and this warmth is because of human actions.
However, during the first term of the George W Bush administration, politicians, commentators and, increasingly the media, dropped the term global warming in favor of climate change.
Why? Well that depends on how cynical you want to be. And how cynical depends on whether you think that the global climate change we are experiencing is due to human action or is just part of the normal scheme of events on a dynamic Earth.
The important thing is to realize that, be it objective fact, concept or fanciful idea, climate can get warmer and it can get colder. It can get wetter or drier; more stormy or calmer; more predictable or more uncertain. And all of these are aspects of climate change that usually do have many, often interacting causes.
The doctors and their spin-doctors were clever. They dropped global warming in favor of climate change when they realized that the consensus view of global warming held the anthropogenic label. Better for them to widen the discourse, otherwise they would be forced by public pressure to try to do something about the warming, actions that would be costly and difficult to agree on. They dropped global warming for the more general and, they thought, less contentious term climate change.
So instead they began to add an adjective and began talking of dangerous climate change or catastrophic climate change … and that is another story.
Interestingly we were not fooled. Currently there are over 3x more Google searches for global warming than there are for climate change. Most of us have understood that the current change in climate is a warm one.