A recent study of Earth's temperature history over the last 2000 years produced some interesting results. But it doesn't provide evidence that humans are changing the climate. In fact, it suggests humans are perhaps only bystanders to what has been going on for a lot longer than 2000 years.
"Global warming is real, scientists warn" proclaims the headline of The Star Ledger, New Jersey's largest circulation newspaper. The story by Kitta MacPherson begins, "A blue-ribbon panel of researchers assigned to provide Congress with a clear analysis of the Earth's surface temperature changes over time has concluded the planet warmed more rapidly over the past 25 years than at any other period in the past 400 years."
All those who jumped to the conclusion that this study confirmed that humans are warming the planet, raise your hand. If you have your hand up, you've been had. Nowhere in the story is there a shred of evidence as to what is causing the warming described in the study. In fact, the purpose of the study was to use proxy methods for estimating temperature history over the past 2000 years in an effort to better understand whether there is evidence for climate change. In limiting its scope to an attempt to reconstruct global temperature history, this study provides no insights into what may have caused variations in temperature history over the period of time studied. Consequently, we know no more than we did before about what has caused prior warming and cooling episodes. It is important to bear this in mind when reading about this study. It is absolutely certain that some groups will try to represent this study as "proving" that humans are changing our climate. Yet no evidence of that claim was provided by this study.
A few things to ponder when considering this as "evidence" for "human-induced" global warming:
The study tried to reconstruct global temperature history over the past 2000 years. Because temperatures were not recorded for most of that time, proxy methods "such as tree rings, coral, ocean and lake sediments, cave deposits, ice cores, glaciers and written records" were used.
Earth's climate history goes back a long way. Let's consider just the period since living organisms existed (about 2.3 billion years) as representative of Earth's history of climate. The study just concluded used proxy methods to estimate global temperature over the past 2000 years. So the period studied amounts to 0.000087% of the climate history during which living organisms have existed on Earth.
As reported, "the panel reported having less confidence in temperature records before the year 1600. Fewer proxies in fewer locations for those periods contributed to that view." So this panel isn't really confident about it's estimated global temperature history beyond the last 400 years! That would be only 20% of the total period studied, or 0.0000174% of Earth's climate history since living organisms have existed.
So based on a study that's looked at only 0.0000174% of Earth's climate history, the headlines "warn" us about some lurking danger of "global warming" that is so bad that we must get Congress to "do something."
The story does provide some opinion that whatever is causing the warming that has been detected, it is not the result of the Industrial Revolution that began about 1860. This comes from the statement by the panel's chairman, Gerald North, who opined, "I think global warming is happening and has been for the last 400 years." Well, if it's been going on for 400 years, then it started well before anyone even dreamed of an Industrial Age.
About 400 years ago much of civilization was experiencing what has been termed The Little Ice Age when temperatures were much colder. Glaciers were advancing, winters were long and severe, and disease was a serious problem. As the Little Ice Age ended, temperatures rose, glaciers began to retreat, summers lengthened, and better farming conditions enhanced health. There have been minor cooling trends spanning several decades over the past 400 years, but it has generally been characterized by a warming emergence from The Little Ice Age.
Climate is rarely static. It is normally either cooling or warming. The long climate history of Earth shows countless cycles of warmth and cold that range from decades to hundreds of years, to thousands of years, to millions of years in duration. Earth's typical climate is much warmer than that which humans have experienced. The last time Earth's typical climate was being experienced was more than 60 million years ago when for several hundred million years there was no surface ice anywhere on the planet except at the peaks of the highest mountains. No polar ice, just tropical, semi-tropical, and temperate climate across most of the planet. This was the climate typical when dinosaurs roamed the planet. In the past 60 million years, Earth has been locked in an Ice Era where temperatures have been typically much colder. Shorter cold periods on the order of hundreds of thousands of years to a few million years are embedded with in the Ice Era and are called Ice Epochs. Warm periods lasting thousands of years within Ice Epochs are interglacials and colder periods lasting thousands of years are known as Ice Ages. Warm and cold periods are common within interglacials and these periods last several hundreds of years. Earth is currently in an interglacial period within an Ice Epoch within an Ice Era. Earth has experienced only seven Ice Eras in its climate history. Ice Eras are typically about 45 million to 60 million years duration. We are at 60 million years in the duration of the current Ice Era. Does this suggest something to you?
Climate doesn't change on a dime. It takes many years of a persistent trend to establish a change in climate. So when we read, "the paper concluded that the 1990s were the warmest decade and that 1998 was the warmest year of the last millennium" we need to recognize that this isn't sufficient to go into "Chicken Little" mode and get frantic about some vague suggestion of dire consequences.
If 1998 was the warmest year of the last millenium, why were 1999 and 2000 cooler if we're in "hockey puck" mode? The "hockey puck" graphic suggests we're heading straight to the moon with global warming ... so why isn't it just as hot as it was in 1998?
There are many reasons to remain skeptical of the concerns about global warming. First among them is that we really do not know whether the warming we've just experienced in recent years is the beginning of another warm period, the beginning of the end of the current Ice Epoch, or the beginning of the end of the current Ice Era. Second, the concerns are usually greatly exaggerated. Suggestions of doom and gloom never quite have realistic details about what to expect. Sea level rises are usually greatly exaggerated from any realistic expectation. The reality is, humankind does much better during warmer climate periods than during cold periods.
Which would you rather contemplate? A period of warmer climate with longer summers and shorter winters? Or a return to an Ice Age with shorter summers and persistent winters?
In any event, climate change takes a long time. A spike in one decade hardly makes convincing evidence of massive change in the future. Particularly when you consider the data we're using is mostly estimated and represents only 0.0000174% of Earth's climate history!
Author of "Looking Out the Window", an evidence-based examination of the "climate change" issue, Bob Webster, is a 12th-generation descendent of both the Darte family (Connecticut, 1630s) and the Webster family (Massachusetts, 1630s). He is a descendant of Daniel Webster's father, Revolutionary War patriot Ebenezer Webster, who served with General Washington. Bob has always had a strong interest in early American history, our Constitution, U.S. politics, and law. Politically he is a constitutional republican with objectivist and libertarian roots. He has faith in the ultimate triumph of truth and reason over deception and emotion. He is a strong believer in our Constitution as written and views the abandonment of constitutional restraint by the regressive Progressive movement as a great danger to our Republic. His favorite novel is Atlas Shrugged by Ayn Rand and believes it should be required reading for all high school students so they can appreciate the cost of tolerating the growth of unconstitutional crushingly powerful central government. He strongly believes, as our Constitution enshrines, that the interests of the individual should be held superior to the interests of the state.
A lifelong interest in meteorology and climatology spurred his strong interest in science. Bob earned his degree in Mathematics at Virginia Tech, graduating in 1964.