AX119_76B9_9.JPG

Former U.S. Vice President Al Gore has spent years warning Americans about human-caused climate change.

(The Associated Press)

Some 98 percent of published climate scientists are convinced that man-made climate change is happening and needs to be addressed now. But the skeptics are persistent, and they've won over many of our country's leaders.

"I'm not a believer in global warming," Republican Party presidential front-runner Donald Trump has said. "And I'm not a believer in man-made global warming." Texas Sen. Ted Cruz, Trump's chief rival for the GOP nomination, agrees. "Climate change is not science," he says. "It's religion."

The Oregonian/OregonLive often reports on the latest peer-reviewed climate-change studies, and so we're often accused of being in thrall to a conspiracy to fool the American people. Climate-change deniers no doubt appreciate Upton Sinclair's famous quote: "It is difficult to get a man to understand something when his salary depends upon his not understanding it." That is, they believe that ever since former Vice President Al Gore made global warming the "it" issue among progressive politicians, funding has flowed to climate-change research with the unspoken expectation that the studies will confirm both the existence of global warming and that humans are the cause of it. This tainted research has led to widespread public misperceptions, they argue.

Of course, climate scientists scoff at the charge that they've been bought and paid for, but again, the skeptics are persistent, and so it is valuable for everyone to know and understand the arguments on both sides of the issue. Are the climate-change deniers actually correct in some of their assertions? You can decide that on your own. Yes, we're encouraging you to do some homework, but we're here to get you started by offering up some of the climate-change deniers' core arguments.

The Earth has always warmed and cooled, skeptics point out. And they insist that the temperature rise over the past century falls within the normal range. "Although the planet warmed 1-1.4degF over the 20th century, it is within the +/- 5degF range of the past 3,000 years," wrote Oregon biochemist and conservative activist Arthur B. Robinson in 2007. (Offers The Guardian in response, stating it's "simple math ...no fancy models needed": "We're headed for about 5degC global surface warming above pre-industrial temperatures by 2100 if we continue on a business-as-usual path. 5degC is the difference between average temperatures now and those during the last ice age. That's not 'small' by any stretch of the imagination.")

Then there's climatologist and well-known climate-change denier Roy Spencer, who exclaims:

"How do [climate-change] scientists expect to be taken seriously when their 'theory' is supported by both floods AND droughts? Too much snow AND too little snow?"

True enough, anyone who reads everyday news articles about climate change will get the feeling that no matter what the weather event, it's blamed on man-made factors. This does seem convenient for those making the case for man-made climate change. But most climate scientists say that, yes, this is simply the way it works: higher temperatures cause more flooding in some areas, increased drought in others and so on.

Now let's consider the arguments of prolific "climate analyst" Fred Goldberg. He insists that the number of weather stations in service in the Arctic declined "rapidly" in the 1990s because the Soviet Union collapsed. This, he says, is the reason for the dramatic spike in the official global average temperature over the past 30 years. "Suddenly there was a heavy unbalance between cold and warm stations, making the warm stations dominate and the global average temperatures skyrocket," he said recently. Could it really be as simple as that? You can watch his entire, hour-long presentation on the video below.

Goldberg also argues that 90 percent of weather stations are on land but that land makes up only 30 percent of Earth's surface, thus throwing off their readings. And he insists that the "urban effect" tilts results toward warming because most weather stations are in cities, particularly at airports, "which collect a lot of heat from planes taking off and landing, so it's not a very good place to measure."

He says there is actually no global average temperature. The average temperature in the southern hemisphere has been constant for the past 100 years, he says, "because we have very cold water circulating around Antarctica, blocking any warmer influence from the north.... In the northern hemisphere we have climate changes due to solar effects and ocean currents."

These arguments, often presented unchallenged because many mainstream climate scientists have decided it's pointless to engage skeptics, have convinced many people. "When will we stop using these trivially wrong contrarian arguments as an excuse for climate inaction?" The Guardian asked in 2014. Serious disagreements on this issue might not ever go away, but it surely will be beneficial if there's a broader understanding of the arguments on both sides, allowing for a vigorous debate based on the science rather than on emotion, economic fear or partisanship.

-- Douglas Perry