Has Global Warming stopped? Not even close.

A recent article in the BBC News claims that Global Warming has stopped in recent years.  In fact, they claim, that there has been no warming over the last 11 years.  Meanwhile, CO2 emissions continue to rise, and climate scientists steadily posit that the climate continues to warm due to greenhouse gas emissions.  So what’s the truth?

Some aspects of climate are relatively simple.  For example, we know that when the greenhouse gas concentrations in our atmosphere rise, the planet warms.  We also know that the burning of fossil fuels is causing the greenhouse gas concentrations in our atmosphere to rise.  Even a seven year old can put these two facts together and conclude that burning fossil fuels causes the Earth to warm.

So why, if the science is so clear, is there controversy?  There are two important answers to this question.

First, there isn’t really a controversy.  As a naturally argumentative profession, never will every scientist agree about everything, but in the case of global warming, there is a clear consensus. Yes, there remain a few fringe scientists that grasp at fewer and fewer straws, desperate to deny that mere mortals could drastically alter their own environment in detrimental ways.  But, in the past three decades, every professional scientific society has released a statement that reflects the consensus view that human activity is warming the planet.  If you aren’t one for consensus, stick to the physical principals.  Either way, you’ll converge on a single conclusion.

The second answer is that the climate system is complicated.  This isn’t a cop-out. We are not asking you merely to take our word for something here, nor are we going to point out that some of these global warming deniers are confused.  Rather, we must understand that while the dominant factor that has influenced climate in the past 40 years has been human activity, there are other factors that still play roles in the yearly swings in temperature.  That is one reason why our annual average temperature is not merely on a straight course right off the top of the charts but varies up and down from year to year.  Accordingly, one must look at longer-term trends than single years to see the effects of global warming.  And one must also understand that weather, the instantaneous state of the atmosphere, is very different from climate, the expected patterns of weather.  It is the patterns here that are changing.

Let’s examine the claims from the BBC article.  First, they claim that the climate has not warmed in the last 11 years.  It is often said that the truth is in the eye of the beholder.  If we choose to ignore all of the data from polar regions, which is where the bulk of the recent warming has occurred, we can see that the climate has not warmed very much.  Include the data from the rapidly warming Arctic (with the rest of the planet), and a different picture emerges.  Several global temperature records exist, but the NASA GISS record (below) has the most complete global coverage, especially in the polar regions.  In the most recent part of the record, where data coverage is most reliable, we can clearly see that there is a continued upward trend in temperature (despite the aperiodic year-to-year swings).


Their other claim is that solar forcing is responsible for the decreased warming.  This may be partially true.  Solar output does play a role in our climate and is included in climate models that project our climate into the future.  These models also include climate coolings caused by volcanic eruptions (which are difficult to predict), and other natural factors that are known to influence climate.

When taken alone, without greenhouse gas emissions, these natural influences on climate do not predict the recent or continued warming (see top part of figure below – black line is the actual measurements).  So, the claims made in the BBC article are somewhat true – changes in incoming solar radiation do not forecast a warming climate in the coming decade and may lead to a cooling.  But add that to human-caused (anthropogenic) greenhouse gas emissions (center part of figure below) and the result (bottom part of figure) is still a warming climate.


So, our climate will continue to vary because of natural forcings (solar, volcanic, etc.) and because of natural cycles in the climate system (El Niño and others), but the overall warming from greenhouse gasses is inescapable unless we take action to reduce our emissions and reduce the concentrations of these gasses in our atmosphere.

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