When discussing evidence about man-made climate change, it’s important to give an honest portrayal of the facts. Just about any set of data can be twisted to give the impression one prefers, right or wrong. One of the main ways this is done is “cherry-picking,” in which one presents only part (sometimes a very tiny part) of the evidence but either ingores or hides the evidence contrary to one’s preference. This is fundamentally dishonest. But it happens a lot these days. When those who deny reality about global warming discuss the facts, honest portrayal be damned.



Suppose, for instance, that when discussing the state of sea ice while testifying at a Congressional hearing about global warming, the only thing I said about it was this:



Global sea ice (both poles) area is currently above normal.



That is not an honest portrayal.

The statement is literally true if by “currently” you mean some particular day in May of 2013, and if by “normal” you mean the 1979-2000 average behavior. But the statement is also an undeniable example of cherry-picking: presenting only the part (a very tiny part) of the evidence which supports one’s preference.

Here’s all the global sea ice area anomaly (amount above or below “normal” for a given time of year) data from the good people at Cryosphere Today:

Notice the trend?

Even if the focus is on very recent data, it’s dishonest not to account for the fact that there is a strong seasonal pattern in how sea ice has changed. Probably the simplest way to counter that “seasonal pattern” thing is by looking at whole years. Here’s the last 365 days for which data are available:

It’s been below “normal” a lot more than it’s been above normal; only 98 of the last 365 days were above while 267 were below. The average for this 365-day time span is -735,000 km^2. Yeah, negative, by more than the size of the state of Texas. For you ferriners who don’t know much about U.S. geography, that’s a big state, 2nd-largest in the USA. Texans like to brag about how big it is.

The highest “above” value was 631,000 km^2 (a bit less than Texas) but the lowest “below” was -2,554,000 km^2 — and that’s more than the area of the states of Texas and Alaska combined. For you ferriners who don’t know U.S. geography, Alaska is a really big state — the old joke says that what annoys Texans most is that if they cut Alaska in half, then Texas would be the 3rd-largest state. Note also that the lowest “below” from last year was the lowest “below” on record.

Because I’m aware of the seasonal pattern in sea ice changes, and I’m also aware of the constant fluctuations that happen all the time, I could have predicted, not only that it might well fluctuate both above and below “normal” but when it might be above (something which is getting pretty rare these days). That’s because not only do I know about that seasonal pattern in sea ice changes, I don’t try to hide it from people.

If you want to give a false impression of what sea ice changes imply about global warming, pick the time of year when global sea ice is above normal so you can say “above normal.” Don’t mention that it’s below normal most of the year, or that when it’s below it’s a lot more so than when it’s above, or that last year’s lowest “below” was the lowest on record. Above all don’t mention the trend, one of undeniable rapid decline. Honest portrayal be damned.

Suppose I also mentioned the state of northern-hemisphere snow cover, but all I said about it was this:



Despite claims of snow being a thing of the past, cold season snowfall has been rising to record levels in recent years.



And on my blog elaborated that claim thus:



Northern Hemisphere Snow Extent Up Sharply Since CO2 Hit 350 PPM – ‘Rutgers University Climate Lab :: Global Snow Lab November to April snow extent was the highest on record this year, and has increased sharply since CO2 hit Hansen’s global warming tipping point of 350 PPM. There is no long term trend, and no indication that snowfall correlates with CO2 in any way’



If you were paying attention to what was said about sea ice, then perhaps you’d be wondering what was not mentioned.

It’s true that there’s no long-term trend for Nov through Apr:

Although the trend line is downward, it’s not statistically significant. But perhaps you’re asking yourself, “Why pick November through April?”

Answer: because that’s the time of year which shows no trend. For an honest portrayal, one must also show what has happened to May-through-October snow cover. Here’s the May-through-October data:

Notice anything?

Yes there’s a trend. Yes it’s statistically significant. Quite.

Who would do such a thing? Marc Morano, that’s who. In testimony at a Congressional hearing, no less.

Perhaps the strangest thing about Morano’s statements is that he began with this proclamation:



I am not a scientist, although I do occasionally play one on TV :) . My background is in political science, which happens to be an ideal background for examining man-made global warming claims.



Really?