My projections about increasing global temperature have been
proved true. But I failed to fully explore how quickly that
average rise would drive an increase in extreme weather.
In a new analysis of the past six decades of global
temperatures, which will be published Monday, my colleagues and
I have revealed a stunning increase in the frequency of
extremely hot summers, with deeply troubling ramifications for
not only our future but also for our present.
This is not a climate model or a prediction but actual
observations of weather events and temperatures that have
happened. Our analysis shows that it is no longer enough to say
that global warming will increase the likelihood of extreme
weather and to repeat the caveat that no individual weather
event can be directly linked to climate change. To the contrary,
our analysis shows that, for the extreme hot weather of the
recent past, there is virtually no explanation other than
climate change.
The deadly
European heat wave of 2003, the fiery
Russian heat wave of 2010 and catastrophic
droughts in Texas and Oklahoma last year can each be
attributed to climate change. And once the data are gathered in
a few weeks’ time, it’s likely that the same will be true for
the
extremely hot summer the United States is suffering through
right now.
These weather events are not simply an example of what
climate change could bring. They are caused by climate change.
The odds that natural variability created these extremes are
minuscule, vanishingly small. To count on those odds would be
like quitting your job and playing the lottery every morning to
pay the bills.
Twenty-four years ago, I introduced the concept of “climate
dice” to help distinguish the long-term trend of climate change
from the natural variability of day-to-day weather. Some summers
are hot, some cool. Some winters brutal, some mild. That’s
natural variability.
But as the climate warms, natural variability is altered,
too. In a normal climate without global warming, two sides of
the die would represent cooler-than-normal weather, two sides
would be normal weather, and two sides would be
warmer-than-normal weather. Rolling the die again and again, or
season after season, you would get an equal variation of weather
over time.
But loading the die with a warming climate changes the odds.
You end up with only one side cooler than normal, one side
average, and four sides warmer than normal. Even with climate
change, you will occasionally see cooler-than-normal summers or
a typically cold winter. Don’t let that fool you.
Our new peer-reviewed study, published by the National
Academy of Sciences, makes clear that while average global
temperature has been steadily rising due to a warming climate
(up about 1.5 degrees Fahrenheit in the past century), the
extremes are actually becoming much more frequent and more
intense worldwide.
When we plotted the world’s changing temperatures on a bell
curve, the extremes of unusually cool and, even more, the
extremes of unusually hot are being altered so they are becoming
both more common and more severe.
The change is so dramatic that one face of the die must now
represent extreme weather to illustrate the greater frequency of
extremely hot weather events.
Such events used to be exceedingly rare. Extremely hot
temperatures covered about 0.1 percent to 0.2 percent of the
globe in the base period of our study, from 1951 to 1980. In the
last three decades, while the average temperature has slowly
risen, the extremes have soared and now cover about 10 percent
of the globe.
This is the world we have changed, and now we have to live in
it — the world that caused the 2003 heat wave in Europe that
killed more than 50,000 people and the 2011 drought in Texas
that caused more than
$5 billion in damage. Such events, our data show, will
become even more frequent and more severe.
There is still time to act and avoid a worsening climate, but
we are wasting precious time. We can solve the challenge of
climate change with a gradually rising fee on carbon collected
from fossil-fuel companies, with 100 percent of the money
rebated to all legal residents on a per capita basis. This would
stimulate innovations and create a robust clean-energy economy
with millions of new jobs. It is a simple, honest and effective
solution.
The future is now. And it is hot.