John Cook, ABC Religion and Ethics, Nov 17 2011

In a much publicised recent speech, Cardinal George Pell strongly endorsed the importance of evidence in public debate. He argues that “the debates about anthropogenic global warming can only be conducted by the accurate recognition and interpretation of scientific evidence.”

It would be hard to find anyone who would disagree with his sentiment – a proper understanding of climate must be built on a foundation of empirical observations. There’s just one problem: Cardinal Pell fails to practise what he preaches.

In order accurately to recognize and interpret scientific evidence, one must consider the full body of evidence. Pell’s arguments make it painfully clear that he is unaware of the many lines of evidence that form our understanding of human-caused global warming.

Decades of scientific research have examined global warming from the front, back, sideways and every other conceivable angle. The same climate myths we hear echoing in the blogosphere, Australian parliament and even in Westminster’s Cathedral Hall – thanks to Cardinal Pell – were scrutinized and discounted by climate scientists years ago, and, in some cases, decades ago.

By ignoring the long history of scientific debate in the peer-reviewed literature, climate skeptics are doomed to repeat the errors of the past.

So, for instance, Pell seems to be ignorant of the full body of evidence when he claims that global warming has stopped. Earlier this year, an international team of scientists headed by John Church from CSIRO tallied up all the energy warming the oceans, heating the land and atmosphere and melting the ice. The measurements show that our climate has continued to build up heat well into the 21st century.

This was hardly news – it confirmed similar research published in 2009. False claims that global warming stopped in 1998 or 2001 (or some other arbitrary date) ignore the empirical fact that our planet continues to accumulate heat.

So how does one make sense of the fact that surface temperature jumps up and down from year to year? Imagine a bath steadily filling up with water. Suppose you place an energetic toddler (let’s call him Enso) into the bath. As the child thrashes about, water sloshes around chaotically. Nevertheless, the average water level continues to rise as the bath fills up.

The same is happening to our planet. The Earth’s heat content is steadily rising but energy is constantly sloshing around between the ocean and the atmosphere, driven by ocean cycles like the El Nino Southern Oscillation (ENSO). To mislead people into thinking we’re experiencing global cooling, misinformers cherry-pick short periods in the temperature record when the warming trend slows temporarily. But the genuine scientific skeptic takes in all the evidence, considers the long-term trends and never forgets the planet’s steady build up in heat.

Cardinal Pell fears that “many politicians have never investigated the primary evidence.” My fear is that Pell himself has failed to investigate the primary evidence that carbon dioxide is causing global warming. The increased greenhouse effect caused by carbon dioxide has been confirmed by many direct measurements made out in the real world.

Satellites measure less heat escaping to space at the very wavelengths that greenhouse gases absorb energy. This is confirmed by surface measurements that find more heat returning to Earth at the very same wavelengths. From this data, scientists concluded:

“this experimental data should effectively end the argument by skeptics that no experimental evidence exists for the connection between greenhouse gas increases in the atmosphere and global warming.”

With the wisdom of hindsight, the scientists’ assumption that skeptics would accept the evidence simply because they were empirical measurements consistent with other, independent observations and confirming our understanding of the science now seems amusingly naive. I’ve since learnt never to underestimate the human capacity to deny inconvenient evidence.

Pell’s lack of understanding of the science is further demonstrated in his ironic argument against the warming effect of carbon dioxide, stating “the atmospheric concentration of carbon dioxide is generally the same everywhere, but temperature changes are not the same everywhere.”

Since the mid-1800s, scientists have predicted that rather than cause identical warming everywhere, the warming effect from increased greenhouse gases should show distinctive patterns. The research comparing observations to predictions was conducted early last decade by Australian scientists, led by Karl Braganza from the Bureau of Meteorology.

The scientists observed that surface temperature over land is warming faster than the oceans, indicating that ocean cycles are not the driver of recent warming. The poles are warming faster than the tropics, ruling out the sun as the primary cause. They found that winters are warming faster than summers and nights are warming faster than days.

If it were the sun, then summers and days would warm faster as that’s when the sun is most powerful. Instead, we observe the predicted outcome from greenhouse warming. All the patterns observed in the temperature record are consistent with human caused warming and rule out natural cause.

Pell’s belief that carbon dioxide should cause temperature to rise the same everywhere ignores 150 years of scientific prediction and confirming observations.

More irony is to be found in Pell’s statement that “notoriously both the medieval warm period and the little ice age were eliminated in the 2001 Third Assessment Report.” The first IPCC report showed temperature jumping around violently over the last 1000 years. In more recent IPCC reports, temperatures during medieval times were shown to be more stable and cooler than current temperatures.

Rather than investigate a scientific reason for the change in medieval temperatures, Cardinal Pell assumes a nefarious conspiracy to “erase the Medieval Warm period” However, close investigation reveals that it is the conspiracy theorists who are trying to hide evidence.

For temperature spanning the last millennia, the first IPCC report used data from a single location in Central England. By the time of the later IPCC reports, more evidence from many other locations had become available and a reconstruction of global temperature was possible.

The extra evidence showed that while certain locations in Europe were quite warm in medieval times, other parts of the globe showed strong cooling.

Again, think of that baby sloshing around in the bath. The water level at a single point will jump up and down violently. But if you consider every point in the bath, the average water level is much steadier.

Similarly, when you average temperature over the entire planet, global temperature does not jump around as violently as it does in a single location in Central England. Globally, the medieval “warm” period was cool compared to our most recent decade, the hottest on record.

So Cardinal Pell’s depiction of events is an inversion of reality. The IPCC didn’t eliminate anything – they included more evidence.

Those who argue for a warmer medieval period are the ones who seek to eliminate evidence by ignoring the global picture. They cite wine growth or flourishing silkworms at specific locations. But these locations don’t all show warmth at the same time. When scientists calculate the average medieval temperature using all the available evidence, they find that warming in one place is roughly balanced by cooling in another place.

According to Cardinal Pell, the basic issue of global warming is “whether the evidence is adequate in that paradigm.” However, we’ve seen that the evidence is not merely adequate – it’s overwhelming.

This begs the question: how is it that Cardinal Pell is unaware of the overwhelming body of evidence. Perusing the sources he cites offers some insight. Pell derives his information from vocal skeptics such as Ian Plimer, Bob Carter, William Happer and Christopher Monckton. He thereby ignores all the research available in the peer-reviewed literature, published by the 97% of climate scientists who agree with the consensus.

Ironically, he doesn’t even draw upon the work of the 3% of skeptic climate scientists. The names referenced repeatedly in his footnotes are not climate scientists and wouldn’t even get in the room. Pell’s “investigation” of the evidence consists of non-peer reviewed writings from a handful of non-experts while ignoring decades of peer-reviewed research by climate experts.

Scripture speaks of the grave responsibility of those who assume the role of teacher and the perils of leading people astray with false teachings. If one elects to pontificate about scientific evidence, they owe it to their readers to survey the full body of evidence to ensure they’re not disseminating misinformation.

Before Cardinal Pell casts judgement on others for not having investigated the evidence, perhaps he should first look to remove the log from his own eye.

John Cook is research fellow at the Global Change Institute, University of Queensland, and creator of Skeptical Science, winner of the Australian Museum 2011 Eureka Prize for the Advancement of Climate Change Knowledge.