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If You Thought 2012 Was Hot, Just Wait a Few Years

It’s already March, but the country is still recovering from last year’s extreme weather and climate events. As the hottest year on record in the U.S., 2012 brought intense drought across the Midwest and Great Plains, record wildfires in the West, and Hurricane Sandy’s path of destruction to the East Coast.

But if you thought 2012 was hot, just wait a few years. Within the coming decades, years like 2012 may become simply “average.” And if we keep emitting CO2 at the current rate, it won’t be long before years like 2012 feel cold.

Average U.S. temperatures are already warmer than they used to be. The 2000s were hotter than the 1990s, and the 1990s were hotter than the 1980s. What’s happening in the U.S. looks like an enhanced version of the global trend, possibly helped by the effects of some natural variations. Scientists have shown that most global warming stems from rising greenhouse gas emissions that end up in the atmosphere from burning fossil fuels. And how those emissions are managed in the coming years will dictate how much hotter it will get this century.

And as future temperatures regularly reach the record levels of 2012, we can also expect to see more of the types of climate extremes that gripped the U.S. last year, including droughts, sea level rise, and more damaging storms.

The good news? Years like 2012 — when the average U.S. temperature was 3°F higher than was typical last century — could be about as bad as it gets.

The bad news? That will only be possible with extraordinary efforts to reduce carbon emissions and significant deployment of technology that captures CO­2 already in the atmosphere (which isn’t even ready for commercial use yet).

Climate Central’s interactive (above) shows that within 10-30 years, a year like 2012 will be an average year in the U.S. And a scant few decades later, typical years will probably be even hotter, perhaps by several degrees.

Climate models can predict how global temperatures will rise this century, depending on how much more CO2 is released into the atmosphere. The climate science research community has recently developed four scenarios for model simulations, each with a different greenhouse gas trajectory. Using these scenarios, it’s easy to see how radically different temperatures might be by 2100. Each line on the graph represents the average of dozens of simulations for each scenario. You can click through the buttons on the bottom of the interactive to see the full range of values for each scenario.

For example, in the interactive graphic above the high-emissions scenario (black) represents a future where greenhouse gas emissions continue to increase through 2100 and the total amount of CO­2 in the atmosphere climbs rapidly. With these kinds of emissions, average annual U.S. temperatures could be more than 7°F higher than what is normal today. Scientists believe that in order to avoid the most serious consequence of climate change, global temperatures shouldn’t rise more than 3.6°F (or 2°C) above the preindustrial average (and, globally, temperatures have risen nearly half that amount already).

Average annual temperature in contiguous U.S.
Click image to enlarge. Credit: Book It: 2012, The Hottest U.S. Year on Record report.

On the other hand, the low-emissions scenario (green) is one where atmospheric greenhouse gas concentrations in 2100 are actually lower than they are today. Of course, that will only be possible if we drastically reduce our emissions and actually remove CO­2 that is already in the atmosphere (which requires technology that isn’t yet viable on a large scale). Even if we took those incredible measures — and as yet there’s virtually no indication we will — temperatures are still going to rise in the next several decades and average U.S. temperatures will probably be at least as high as they were in 2012.

The other two medium-emissions scenarios (blue and red), fall somewhere in the middle. They illustrate a future where greenhouse gas emissions eventually stop increasing, but the total amount of greenhouse gases in the atmosphere continues to grow. The scenarios differ on when emissions stabilize, but the effect will be similar: rising temperatures through 2100.

So where do we stand today? Our current trajectory is close to the black high-emissions scenario. If we stay on this path without curbing emissions, we can expect to regularly see average temperatures at least 7oF higher than we do today. And with that will come more weather extremes, droughts, wildfires, sea level rise, and more destructive force from hurricanes like Sandy.

Even with action to help mitigate climate change, the interactive shows just how sobering these numbers truly are. All that CO2 we’ve already added to the atmosphere will keep temperatures climbing for several decades. Under any imaginable scenario — even in the best-case scenario — soon we’ll likely see years like 2012 much more regularly.


In order to determine when last year’s record-breaking temperature will be that of an average year, we looked at how much climate models(2) predict average U.S. temperatures to rise this century. Using global simulations of four potential greenhouse gas emission trajectories (the Representative Concentration Pathways(1)), we’ve calculated future average global temperatures (for each trajectory). We have then estimated future average U.S. temperatures by scaling the global temperatures according to a factor calculated on the basis of the ratio of global temperatures to U.S. temperatures by the end of the 21st century, which has been shown to apply reasonably accurately to other periods during the length of the simulation, according to the method known as “pattern scaling”(2). The method is not supposed to predict exact year-by-year changes, but it is appropriate to get a sense of the long-term trends in mean temperatures at regional scales (U.S. average-scale) and thus can give us a good estimate of the time frame — on the order of a decade or so — by which temperatures in the U.S. will reach the threshold represented by this year’s anomalously warm temperature.

We acknowledge the World Climate Research Programme's Working Group on Coupled Modelling, which is responsible for CMIP, and we thank the climate modeling groups for producing and making available their model output. For CMIP the U.S. Department of Energy's Program for Climate Model Diagnosis and Intercomparison provides coordinating support and led development of software infrastructure in partnership with the Global Organization for Earth System Science Portals.

Special acknowledgments also to Julie Arblaster (University Corporation of Atmospheric Research and Australia’s Bureau of Meteorology), who assisted Climate Central with computations.

1 Santer, B. D., T. M. L. Wigley, M. E. Schlesinger, and J. F. B. Mitchell, 1990: Developing climate scenarios from equilibrium GCM results. Max-Planck-Institut-für-Meteorologie, 29 pp. pp.

2 Calculations were based on the model simulations from CMIP5, the most up-to-date series of climate model simulations, which were used for the upcoming IPCC 5th Assessment Report.

Related Content
NOAA: 2012 Hottest & 2nd-Most Extreme Year On Record
Warming Winters: U.S. Temperature Trends
Can U.S. Carbon Emissions Keep Falling?


By Stephen Hendrickson (Dayton WA 99328)
on March 20th, 2013

This will end the debate once and for all..

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By Dave (Basking Ridge, NJ 07920)
on March 20th, 2013

It’s a great article (thanks) and the center piece graphic / data is impressive. But, after all the work that must have gone into generating that, I think you have understated what it tells us.  For instance, a bold red horizontal line at 3.6F (2C) on this graph could emphasize that this level roughly demarcates two entirely different global regimes which have profoundly different characteristics and consequences. The importance of that with respect to tipping points (DAI) is well known and not to discuss it here is an omission.

Most experts now expect that a high emissions scenario is the most likely because current global emissions are the highest ever and are increasing with no evidence yet of when they will even peak. One can argue about that of course, but it looks pretty likely.

So, another title for this piece could also be: Hey parents, if you haven’t taken the kids to see a real world living coral reef yet try to do that soon because if you don’t then by the time they have grown up the reefs will no longer be there.

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By R. Elton-Bott
on March 21st, 2013

A new colour, purple, for daily temperatures at or above 50 degrees C, was added this year to temperature charts in Australia by the Bureau of Meteorology.  With climate change, all cities adjoining deserts are now vulnerable as maximum temperatures during heat waves have hovered between 46 and 48 degrees C for several days this year.  Soon, evacuations of young children and older folks, from cities experiencing 50 degrees C or above for more than a day or two, is now a distinct possibility.  Certainly, charts with increasing trends of average temperatures are needed, but should show too the increasing trends of maximum temperatures reached, which are a much more dangerous aspect of climate change.  We must move back to 350 ppm atmospheric CO2 quickly before forest ecosystems deteriorate.  Global forests are hungry for nutrients and will respond strongly to even small amounts of aerial-applied fertilizers.  Forest sequestration of CO2 would be eminently quicker, cheaper, and safer than other methods of CO2 sequestration.

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By sailrick (San Rafael/CA/94901)
on March 21st, 2013

I think there’s a typo here.

“global temperatures shouldn’t rise more than 3.6oF (or 2oC) “

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By Steve Goddard (Fort Collins Colorado 80525)
on March 21st, 2013

US temperatures are below normal so far this year, and March temperatures are the coldest since 1969.

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By Adam (Toronto)
on March 21st, 2013

If you look closely, and are pessimistic like me, you’ll note that we could cross the threshold of 3.6 deg F (2 deg C) by 2029.

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By A C Osborn
on March 21st, 2013

Steve Goddard, have you noticed how the extreme temperatures of the 1930s (Dustbowl) have been disappeared?
Classic warming technique that bears no relation to reality or history. Must have used GISS.

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By Dave (Basking Ridge, NJ 07920)
on March 22nd, 2013

I agree with your sentiment in that, particularly in view of what is at stake here, then to interpret and act on this kind of information responsibly one must also consider the implications of a reasonable worst case, as well as more optimistic scenarios. That’s common practice for a lot of other types of risk assessment – and makes sense here as well.

My own comment (and earlier) in relation to the all too briefly mentioned 2C DAI level (which apparently may also more accurately be 1.5C) is to underscore that the general climate change problem is not just about the temperature going up a bit, sea level rising a bit and the weather deteriorating a bit. It is not a one dimensional kind of thing that one can easily encapsulate in curves on simple graphs. It has to do with approaching and entering a new and non linear climate regime which is very different from the one we are in right now. That is the really big deal. It is much more than a new normal. In this context, it is an unstable region with profound consequences. As interesting as this report is as it stands, I think it fails to achieve full value by not conveying that relevant point. In my opinion, not doing that makes the report and top graph look to me more like a long range weather prediction. This is Climate Central – not weather central.

Of course, the +2C level we are discussing is technically on a different and offset temperature scale compared with the top graphic presented here because of definition differences. CC, with access to the model used here, could probably estimate or comment better on the correction – but I am certain it will fall in that same data range.

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By SidAbma (Atascadero,CA,93422)
on March 23rd, 2013

Natural gas according to the last meeting of the World Energy Congress is going to be the worlds most important energy source. Changing coal and heavy oil to natural gas will already make a big difference in emissions.

But natural gas can be consumed so much more efficiently than is being done today. How many chimneys are poking out of the roofs of commercial buildings and industry? What is coming out of all those chimneys?
HOT Exhaust. Lots of hot Exhaust.  Why?
Natural gas is an energy source that can be consumed to well over 90% energy efficiency.

The technology of Condensing Flue Gas Heat Recovery is designed to recover the heat energy out of this natural gas exhaust, making this recovered heat energy available to be used inside the building or facility as space heating, or put into heating the domestic or industrial plant process or washdown water. At a hotel or university this heat energy can be used to heat the swimming pools.
Leaving the Condensing flue gas heat recovery unit will be COOL exhaust.

Increased natural gas energy efficiency = Reduced utility bills = Profit
Increased natural gas energy efficiency = Reduced global warming
Increased natural gas energy efficiency = Reduced CO2 emissions
Increased natural gas energy efficiency = Water conservation

The DOE states that for every 1 million Btu’s of energy recovered from these waste natural gas exhaust gases, and this recovered heat energy is utilized in the building or facility, 118 lbs of CO2 will NOT be put into the atmosphere.

What could this do for our environment?

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By Michael D Smith (Near Chicago, IL 60491)
on March 24th, 2013

Scientists have shown that most global warming stems from rising greenhouse gas emissions that end up in the atmosphere from burning fossil fuels.

When did they show that?  If they were able to SHOW that, it would be an impressive contribution to science.

1) When was this shown?
2) By whom?
3) Source?


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