Climate change has been a polarizing topic of science often debated within the least logical forums of politics.
In recent years, the battle between the two sides has converged on weather models, with naysayers pointing out such simulations have failed to accurately project increases in temperature since 2000.
A recently published study out of SUNY Albany states there’s a reason behind the warming “hiatus” observed since then. But, those behind the study don’t find comfort in the results.
Atmospheric greenhouse gases continue to rise during recent years, yet global-mean surface temperature have not shown the same rate of warming as climate models have shown in the past. This slowdown in surface warming, often referred to as the global warming “hiatus,” contrasts model simulations, which on average show strong warming since 2000.
A new University at Albany study published in the April 13, 2015, issue of Nature Climate Change links the Inter-decadal Pacific Oscillation with essentially all the difference between observed and model-simulated global warming rates on decadal time scales since 1920, including the warming hiatus since 2000.
The study, led by UAlbany Associate Professor Aiguo Dai, includes co-authors, Dr. J. C. Fyfe of Environment Canada, Prof. Shang-ping Xie of UC, San Diego; and Dr. Xingang Dai of Institute of Atmpsoheric Physics/Chinese Academy of Sciences (IAP/CAS). Together the team analyzed, observed and model-simulated global temperature data and quantified the contributions of internal climate variability to decadal changes in global warming rate since 1920.
Dai explained to The Spotlight that the study took approximately one year. Its focus was to address the discrepancy between temperatures prognosticated through computer models and observed global temperatures. The difference between the two has attracted attention as it has undermined the credibility of these models.
“Naturally, people would ask the question: if the models cannot simulate the current global warming rate, how can we trust their projections of future climate change?” said Dai. “This is a very reasonable question that deserves a satisfactory answer from the climate science community. The global warming hiatus has also been used to dismiss climate science entirely by some deniers of global warming. Thus, explaining the warming hiatus has become an urgent task for climate scientists.”
Recent studies have attributed the warming hiatus to decadal cooling in the tropical Pacific, intensifying trade winds, changes in El Niño activity, increasing volcanic activity and decreasing solar irradiance that have not been adequately accounted for in model simulations.
Dai said the study shows that the Inter-decadal Pacific Oscillation, a prominent natural mode of multi-decadal variations in Pacific sea surface temperatures, has been associated with large temperature anomalies over both ocean and land. Combined with another leading measurement of internal climate variations, the Pacific oscillation explains essentially all the difference between observed and model-simulated global warming rates on decadal time scales since 1920, and in particular the warming hiatus since 2000. The spatial patterns of the Pacific oscillation-induced temperature changes match observations, but differ from those associated with greenhouse gas-induced warming or aerosol-induced cooling.
“This finding is consistent with other recent studies and supports the notion that the recent warming hiatus resulted primarily from natural climate variations, rather than from aerosols or other causes missed by the models,” said Dai.
Climate models still have difficulties in simulating observed Pacific oscillation and other natural climate variations due to deficiencies in model physics and model starting conditions. Thus, discrepancies between observed and model-simulated global warming rates on decadal time scales should be expected, rather than taken as surprises.
“The model-versus-observation discrepancies do not imply that the model-simulated climate change due to rising greenhouse gases and other anthropogenic forcing is wrong,” said Dai. “Recent history suggests that the Inter-decadal Pacific Oscillation could reverse course soon. Should that happen, we may see accelerated global warming rates in the coming decades.”
When people speak of climate change, they often refer to the weather, as it is happening today. Dai said the difference between climate and weather observations is measured in time.
“The climate usually refers to a multi-year average, or 30-year mean temperature, or 30-year mean precipitation at the airport, a 30-year trend,” said Dai, whereas “weather” is what is happening outside now. “They are related, but they are not the same.”
The other side of the debate, though recognizing the planet is warming, does not necessarily agree that the global climate is changing for the worse.
“Just because we have an extreme weather event, it doesn’t necessarily mean that global warming is to blame,” said James M. Taylor of the Heartland Institute, speaking from a podcast released by the think tank shortly after Hurricane Sandy slammed the New York City metropolitan area in October 2012. “Just about any extreme weather event that we measure, we see that as our planet has gradually warmed, as we recover from the little ice age – which ended a little over 100 years ago – we’ve seen fewer of these events, and they are less extreme.”
Taylor is also managing editor of Environment & Climate News, a national monthly publication devoted to sound science and free-market environmentalism with a circulation of approximately 75,000 readers.
“During the 1950s, during just a two-year span, there were a number of strong tropical storms that slammed into the Northeast at that period,” said Taylor. “So, when folks now say that ‘We’re having weather events now that never occurred before, This is a new thing, Don’t try to say it’s not Global Warming, or that this isn’t the new normal.’ Well, actually, just because our memories don’t go back to the 1950s, we’ve been blessed with climate, with weather, during the past several decades that has been remarkably benign. Beneficial to civilization. Beneficial to human welfare, as our planet has warmed.”
Since Al Gore’s 2006 documentary “An Inconvenient Truth,” the general public has become familiar with the “hockey stick” graph with data points of recorded global temperatures rising over the past century. However, news of such warnings date further back.
In June 1989, U.S. Environmental Protection Agency Administrator William K. Reilly stated greenhouse gases as the cause for global warming, and that it posed as one of “the most serious and intractable problems” to the world. In the L.A. Times article that appeared June 28, 1989, Reilly expressed doubts that any effort would be made to confront the issue, despite predictions of increased droughts, melting polar ice caps, raising ocean levels, compromised shoreline communities, and the destruction of island habitats.
A quarter century later, with exceptional droughts reported throughout the western continental United States, melting polar ice caps, and island civilizations threatened by rising sea levels in the South Pacific, Reilly’s prognostications remain intact.
