If we don't begin phasing out fossil fuels this decade, temperatures will rise to unlivable levels within the lifetimes of our children.

If we don't begin phasing out fossil fuels this decade, temperatures will rise to unlivable levels within the lifetimes of our children.

The most commonly asked question about global warming is, “How hot is it going to get?” This important question deserves a clear and simple answer. But the science of climate change is complicated and it is not easy to answer this important question simply. I believe the main reason voters don’t list global warming as their top issue is because they do not know how hot it is going to get. If Climate Hawks want voters to vote for climate action, we must answer, “How hot is it going to get?” And our answer must be clear, consistent, and simple.

The Climate Hawk movement sprang from the scientific community and we communicate in the language of science. And this has been our gravest error. When scientists talk about global warming, they talk about the increase in the average temperature for the entire Earth. And this global average is a combination of summer, winter, day, and night. And scientists usually talk in Celsius, not Fahrenheit. Their supercomputers forecast Earth’s average temperature increasing from 2 to 12 degrees Celsius depending on the year. To most Americans, this does not sound terribly threatening. And the fossil fuel industry and climate deniers have taken great advantage of this ambiguity.

So we need to cut through this ambiguity and be clear about how hot it will get. First, for the American audience, we should communicate mostly in Fahrenheit, not Celsius. Second, we should focus less on describing the average temperature for the entire Earth. People don’t think in average temperatures. If someone asked you, “How hot was it yesterday?” Would you answer, “The average temperature was 33.6 degrees Celsius.” No. You would simply answer, “The high was 105F degrees and the low was only 80F degrees.” This is the type of answer people expect when they ask, “How hot is it going to get?”

Now I recognize that answering the question, “How hot is it going to get?” is complicated because it depends on where you live, what future year you are talking about, and how much carbon we burn between now and then. These are important details. But most people are not scientists and don’t really care about these nuances. They just want to know ‘How hot is it going to get?” Or, in other words, “Will this be a problem for my kids?” So I believe the best answer is the highest possible temperature that will result from global warming.

But there is one important caveat. The Heat Index. As the Earth warms, the atmosphere will hold more water vapor than before, and this increase in humidity will push up the heat index all around the globe. So a 90 degree Fahrenheit day in Atlanta in the year 2100 will be much warmer (have a higher heat index) than today because humidity levels will be much higher. So Climate Hawks should include the Heat Index when describing how hot it will get in the future.

So answering the question, “How hot is it going get?” is quite simple. If we keep burning fossil fuels, temperature will eventually reach 147 degrees Fahrenheit with a heat index of 200 degrees (or more) Fahrenheit where many people now live.



That’s it. Simple. Clear. Terrifying.

Climate deniers will accuse us of using the Heat Index to exaggerate the true future heat, but they are going to do that no matter what we say. And the heat index IS a better measure of how hot it is going to get, so we should use it. Climate deniers will also argue that today some desert locations reach very high temperatures. But we must push back and say few people live in these locations because it’s just too hot. And in the future, even higher temperatures will become common in places where millions if not billions of people live today.

There have been several scientific papers exploring the maximum temperatures that will result from global warming. And to better understand these papers, I reached out to a climate scientist who co-authored the famous ‘wet-bulb’ study. And with his assistance through email, I created this simple chart which is an APPROXIMATE range for the maximum temperature and heat index on a warming Earth.

Approximate Estimates for Maximum Fahrenheit

Temperatures and Heat Index on a Warming Earth Increase

in Earth's Approximate Maximum

Average Celsius Fahrenheit Heat Wave

Temperature Temperature Heat Index

+12 C 147 F 200 F

+6 C 136 F 170 F

+4 C 132 F 155 F

+2 C 129 F 142 F

Now I violated my own suggestions in this chart because I included the Celsius change in temperature for the entire Earth. And I did this because of the upcoming 2015 Global Climate Change negotiations in Paris this December. At this conference, governments of the world will decide if we should phase out fossil fuels quickly and keep the climate we have today. Or, if we should phase out fossil fuels more slowly (if at all) and allow Earth’s temperature to rise. In the coming months, the media (hopefully) will report on these scenarios and the media will describe them as +2C, +4C, and +6C changes in Earths average temperature.

And unfortunately, the discussion will end there. Because the media will not report to their audiences the consequences of allowing Earths average temperature to increase +2C, +4C, or +6C. Those consequences are in the center and right columns in the chart above. Our challenge as Climate Hawks is to force the media to highlight the heat index in the right column. This column clearly shows that any significant warming in Earth’s average temperature is not acceptable. It is simply suicide.

Another important caveat about the center and right columns is that these maximum temperatures will occur in rare super heat waves. These won’t be the daily high temperatures year round. And again, climate deniers will certainly push back against these temperature projections and say that they are not important because they will be rare. But that’s like saying a full scale nuclear war would not be a big deal if it only happened just once in the next 50 years. And global warming is a lot like nuclear war. Because a single summer of 129F degree days and a 142F heat index would turn our farms to dust, burn many of our cities to the ground, and would surely destroy most of God’s Creation. Forests, creeks, rivers, grasslands, marshlands, and all life found within them. Gone. Forever.

Children alive today may very well live to the year 2100. And, if we don’t begin a rapid phase out fossil fuels this decade, Earth’s average temperature will rise +6C in their lifetime. This means 136F heat waves with a 170F heat index. And if Earth's average temperature increases +6C, the runaway Arctic permafrost melt and methane feedback loop would be inevitable. And that will push Earth’s average temperature up +12C by 2300. End result, not much life on Earth.

There is no sane reason why we should ‘settle’ for any increase in Earth’s temperature. And leading up to the Global Climate Change Conference in Paris this December, Climate Hawks need to clearly and simply answer the question, “How hot is it going to get?” On blogs, social media, big media websites, at church, and especially in communications with politicians at ALL levels of government. Because if we want the public to demand climate action, the public needs to know how hot it is going to get.