Is a global temperature change of 0.6C significant?

Question

The global temperature dropped more than 0.6C from Jan 2007 to Jan 2008. See it here:

http://wattsupwiththat.wordpress.com/2008/02/19/january-2008-4-sources-say-globally-cooler-in-the-past-12-months/

When the skeptics claim that this is a large amount of cooling. the global warming believers say that 0.6C is normal year-to-year variation.

The global temperature changed about 0.6C in the 20th century.

Does a 100 year trend equal to year-to-year variation prove a looming catastrophe?

Is a global temperature change of 0.6C significant?

Answer 1

"Is it fair to say that 0.6C in one year is "in the noise" and also say that a 0.6C trend over 100 years is significant?"

Yes, you've hit the nail on the head.  One year doesn't disrupt our climate, which affects where we live and how successfully we live there: precipitation and water supplies, crop growth and survival, forest survival, disease-carrying pest range and survival, and so on.  

Unfortunately CO2 is a slow influence that stays in the atmosphere for 1000+ years, and we've only seen 50% of the warming that will come from the CO2 that was in the atmosphere in the 1950s and 1960s (plus some smaller portion of the damage from what was in the air after that).

We have a lot more warming to come already, and it will take us decades to stop our growth of CO2 emissions, let alone reduce them, so in no way is the urgency limited to concern about that first .6 degrees C (1 degree F) that's now in our rear view mirror.

In short, weather doesn't affect our survival globally, climate can, especially if we wait to see what happens.

To illustrate the concept of CO2 warming momentum, if you're driving down the road at 55MPH/100KPH and it appears that you're likely to hit a concrete wall, do you wait to see the first foot of your front end crumple before you hit the brakes?  

What if you can already see the first inch of impact, do you wait for that next foot of impact before you try to minimize the damage and stop the engine from severing your legs?

Answer 2

A 0.6 degree drop in trmperature during one year is not that dangerous. That being said, we are due for a cooling trend as it has been 12000 years since the last recorded ice age. Although this does not seem like a large drop in temperature, it could signify the beginning of a cooling trend, or an increase of efficiency in reducing global warming. If the temperature continues todrop on an annual basis for the next decade, then there is cause for concern.

Answer 3

The problem is that the alleged temperature increase over the previous 100 years has been wiped out in 1 year.  The baseball analogy is a red-herring at best.  A better analogy would be that a batter's normal average is .250.  The batter goes on a hot streak (no pun intended) and gradually increases his average to .260, .270, .280.  He is now a .280 hitter, but he goes 0 for 50 and drops his average back to .250.  Sorry to burst the bubble, but no matter what anyone says, he is a .250 hitter and to get back up to .280 or .290, he is going to have go another hot streak, but that ain't guaranteed.  For all we know, he could go 2 for 30 and drop his average even lower to .240.

The sad fact is that the alarmists are now reduced to holding onto whatever they can to continue to support a theory that is falling apart around them.  We are getting closer and closer to reaching the dates where they say specific things are going to happen and those things are not happening.

On top of all of this, what does an increase of .6 or a decrease of .6 really mean?  Who has come up with the "normal" temperature that we use for the comparison?  And how do we know that the "normal" temperature is really the "normal" temperature?  We have around 100 years of somewhat accurate weather data and only a few decades of accurate worldwide temperature data.  Variations of a degree or 2 would not be out of the question when considering the sources of temperature readings.  How do we know that we aren't warming up to the "normal" temperature?

Answer 4

The temperature varies so much every year, a 0.6C change is not too much in the perspective of things, especially because over the last 1000 years, the temperature average has fluctuated constantly, with the medeval warm period and the little ice age. So as I see it, there is no real catastrophe if the temperature rises/falls by 0.6C

Answer 5

"Is it fair to say that 0.6C in one year is "in the noise" and also say that a 0.6C trend over 100 years is significant?"

Start by using the proper temperature scale.  Without the sun, the earth's temperature would be near absolute zero.  Let's use a temperature scale that starts at absolute zero so that we can see how much heating has occurred.  

The earth is heated from near absolute zero to about 288 degrees K (15C) by the sun, CO2, clouds, whatever.  It then warms up an additional 0.6 degrees K (K and C degrees are the same size) from CO2 (or not CO2 depending on who you believe).  Let's see how big that change is:  

0.6 / 288 = 0.002

Thats 2 parts in 1000 or 0.2%.  

The 20th century warming and 2007 cooling both represent a 0.2% temperature change.  

Everyone should (but won't) admit that 0.2% represents a really small change in temperature.

As for the analogies, they're bogus:

If the 2007 heat was stored within the earth (dirt or ocean, it's not in the atmosphere), there will be a tendency for global temperatures to revert back to mean (go back toward the recent average) because the heat is still here.  If the heat escaped to space (albedo, solar irradiance), we have established a new global mean temperature because that 2007 heat is headed toward the stars, never to return.

If the mechanisms are the same as recent years, we should expect reversion to the mean.  If that does not happen, we need to open a new chapter in the global warming book and try to figure out what is going on.

To the original question, we should agree that a change 0.2% (0.6C) is not significant whether it occurs in 1 year or in 1 century.

Answer 6

And the global temperature jumped up 0.76 C from Feb 1994 to Feb 1995, so what?  Month to month comparisons are useless when your talking about climate change.  That's simply weather and short-term noise, in this case most likely caused by the current La Niña event (cold deep ocean water cools the surface, causing a short-term drop in the average temperature).

The 12-month average (2/2007 - 1/2008) is still 0.504 C above the 1951 - 1980 average.  And it's still warmer than 2000, 1999, 1997, and every yearly average before that in our instrumental record.

And since you link to Anthony Watts article, you should know that he doesn't even seem to understand basic numerical analysis or statistics (guess that's why he was on TV/radio and not doing research):

http://tamino.wordpress.com/2008/03/02/w...

Answer 7

Look, it's not like global warming just concerns day to day weather fluctuations and whether or not you have to wear a tank top earlier in the year. That's just simplifying and trivializing an issue, and you should know better, or at least get your facts straight.

Global warming concerns the effects these "small" increases in temperature are having the world over.

Here's one example and I want you to just hear me out without trying to deny it first chance. Dengue fever is a disease caused by a virus that is spread by mosquitos. It used to only be found in areas with tropical climates, like through Asia and Africa.

A slight increase in temperature worldwide has now allowed these mosquitos to spread further, and live in regions that they previously could not.

Now we are seeing dengue fever in SOUTHERN EUROPE, which had until now been unaffected by these horrible disease.

You know what? I know this won't change your mind. You're going to keep on denying global warming is happening for as long as you live. You'll keep on reading select articles that skew facts, and ignore the huge mass of material and research that points to anything you don't want to hear. You'll bury your head in the sand and just wait.

Good luck with that.

Answer 8

Depends on the time scale involved (a common thing in science).  You simply need to look at ALL the data in context.

Weather factors can overcome global warming for a short time.  It happened in 1982, 1991-1992, 1999-2000.  EVERY TIME global warming came back stronger than ever.  Proof.

http://data.giss.nasa.gov/gistemp/2007/

discussed in detail, with confirmation, at:

http://tamino.wordpress.com/2008/01/24/g...

There's a reason this is not front page news, and it's not some paranoid "conspiracy".  The Earth has been there, done that, in recent history.

As long as we keep making greenhouse gases in enormous amounts, global warming will dominate in the long run.  It's simple physics.

http://earthguide.ucsd.edu/earthguide/di...

Answer 9

Baseball analogy.

Bob Smith is a lifetime .250 hitter.  On the average he hits 1 for 4.  There are days when he hits 0 for 4, and other days he might hit 2 for 4.  But overall he goes 1 for 4 for a .250 average.  

This is kind of like temperatures - you will expect some years the temperature to be below the average, and other years when the temperature will be above the average, but if everything is equal then the temperature will not rise over a century.

One off season, Bob takes steroids.  He still has games where he goes 0 for 4, and still has games where he goes 2 for 4, but now there are more games where he goes 2 for 4.  Overall his average on the year goes up from .250 to .275.

With the addition of greenhouse gases to the atmosphere, it is like putting the climate on steroids.  There were will still be years when the global temp goes down, and years where the global temp goes up - but overall, the temp over a century will rise.