Five experts discuss the facts and gaps:
Climate change: What, how and when?
Five Norwegian researchers discuss climate change and its ramifications for society from their different scientific perspectives. One thing these experts all agree upon is that people are largely responsible for the changes.
Jenny Bytingsvik (Photo: Bård Gudim)
“We realise that we still know too little to make accurate estimates of what changes we can expect, how quickly, and what impacts they will have on humans, animals and plants,” says Ph.D. candidate Jenny Bytingsvik, a researcher in physiology and marine sciences at the Norwegian University of Science and Technology (NTNU) in Trondheim.
Species will have to adapt
“What concerns us ecotoxicologists most is whether species will be able to adapt to climate change – and whether pollutants may weaken animals’ ability to adapt. A number of chemicals have been shown to have negative effects on hormones that are essential for growth, development, behaviour, the immune system and reproduction in animals.”
“In recent decades, rising temperatures and other changes in climate have led to shifts in the distribution of some animal species,” explains Ms Bytingsvik. “Some mobile species have migrated to new, cooler areas – but for species already living in the polar regions or high elevations, that is simply not possible.”
“What’s more, we know that the climate is changing more rapidly in the polar regions than other areas of the world. Impacts we are seeing now include a reduction in the annual duration of sea ice, its coverage and its thickness. Polar bears and several species of seal need the sea ice in order to hunt for food and to reproduce. So the issue is, will these species be able to adapt to the sea ice diminishing, or will they become extinct in the next 50 to 100 years?”
Rising consequences
Jan Gunnar Winther (Photo: Ole Magnus Rapp/Aftenposten)
“The climate has always fluctuated,” points out Jan-Gunnar Winther, Director of the Norwegian Polar Institute. “But we know – with more than 90 per cent certainty – that humans are responsible for the rapid climate change we are experiencing. We also know that the longer we wait to take action against it, the more severe the impacts will be.”
“One of the most convincing pieces of evidence that the climate is warming is that summer ice in the Arctic is disappearing at a record rate. Our climate models were not able to predict this happening so quickly. They also underestimated how rapidly the massive Greenland Ice Sheet would now be melting.”
“Now the main uncertainty is how much the melting of Greenland’s ice will raise sea levels,” Dr. Winther explains. “There is also uncertainty about the future impact of permafrost thawing. As permafrost thaws, methane and carbon dioxide are released, which could be a major driver of further global warming. But we still don’t know enough to say how quickly that will happen.”
There is broad agreement among researchers concerning the climate issues of our time. Below the surface, however, lie many nuances of opinion. (Photo: Shutterstock)
“We also don’t know much about the consequences of the melting of the Antarctic Ice Sheet, by far the largest mass of ice on earth. The melting and fragmentation of the floating ice shelves that surround the continent can indirectly affect global sea level, since this allows the inland glaciers behind them to flow faster into the sea, where the ice melts. But we still don’t fully understand the dynamics,” emphasises Dr Winther.
Uneven warming
Jan Ove Hagen (Photo: UiO)
“There is no doubt that it has become warmer in recent decades,” says Jon Ove Hagen, Professor of physical geography/glaciology at the University of Oslo. “Glaciers around the world are in decline – but the rate of warming is not uniform. Some regions are undergoing less rise in temperatures while others are warming more rapidly. The glaciers are responding directly to a warming climate. In many places around the world, glacier decline has accelerated in the past 10–20 years.” According to the glaciologist, there is no other explanation than that it is getting warmer.
“There is much uncertainty, even in the explanatory models. We don’t know to what extent the changes in climate are due to anthropogenic emissions. And there is uncertainty about the future trends in emissions of various greenhouse gases – not only those related to human activity but also natural emissions from permafrost zones, where vast amounts of greenhouse gases could be released should the permafrost thaw.”
When it comes to the glaciers, it is very uncertain how Greenland and Antarctica will be affected by an even warmer climate,” says Professor Hagen. “Conditions in Greenland over the next 50 to 100 years will be critical for what we can expect in terms of changes in sea level. We are also studying whether what is being observed in Greenland will continue, namely the dynamic response of faster-flowing ice streams and increased rate of calving, and whether similar responses may occur for other glaciers that end at the sea.”
Climate change through the ages
Hanne Christiansen (Photo: Ole Humlum)
“We know that climate change has been occurring throughout the geological history of the earth,” adds Professor Hanne Christiansen. “But it is only in the past 100 years or so, a short period geologically speaking, that we have been collecting direct meteorological measurements in the Arctic regions. For large areas, we only have measurements for the past 50 years.” She conducts research on permafrost and the development of permafrost landscapes at the University Centre in Svalbard (UNIS).
“In the cryosphere, especially in the permafrost, we only have a few, even shorter, time series for temperature. Not until the International Polar Year (IPY) 2007-2008 did we begin measuring temperatures in several of the permafrost landscape types. So since we only have about one year’s data from those,” she points out, “we are far from knowing everything about the variations in permafrost thermal conditions.”
“Several parameters affect permafrost temperature: air temperature, amount of snow cover, distribution of snow and how long it remains, wind, vegetation, and type of sediment and rock. We also know that on mainland Norway there is “warm” permafrost, meaning that the temperature is around the freezing point, while Svalbard’s permafrost is colder.”
“We still lack sufficient knowledge about how the various meteorological and local parameters combine to affect temperatures in the permafrost of several other permafrost landscape types. So far, we have only mapped the extent of permafrost in detail in a few areas of Norway. Fortunately,” concludes Professor Christiansen, “the permafrost observatories we established during IPY will give us more data and enhance our knowledge in the years ahead.”
Models need refining
Ole Anders Nøst (Photo: Per Gunnar Gabrielsen)
“We still don’t understand the dynamics of earth’s climate especially well,” states Ole Anders Nøst, who conducts research in physical oceanography at the Norwegian Polar Institute. “We have models that can simulate climate processes, but models are limited by the substantial gaps in our knowledge. Nevertheless, current climate models are the best tools we have to work with right now, and they are being improved continually. The models are predicting a warmer and wetter climate with more extreme weather. But can we trust them?”
“The deeper we go into climate dynamics, the more we realise we don’t understand. And we see that there are many important processes that the climate models cannot deal with; the resolution of all the current models is too poor. So,” asks Dr Nøst, “could they all be making the same mistake?”
“In order to answer that, we need to enhance our understanding of climate dynamics,” he believes. “The models are predicting warming based on rising levels of CO2 in the atmosphere. But there is disagreement on the sun’s role, and there is further disagreement on how variations in the sea affect atmospheric temperatures. What’s more, we don’t yet understand how ocean currents transport heat, and we don’t fully comprehend cloud physics. No one can say with certainty that they truly understand what is happening to the earth. We have a good idea of how the global temperature has fluctuated over the past 100 to 150 years,” concludes Dr Nøst, “but I am not at all convinced that we understand the causes of these fluctuations.”
From Forskning magazine no. 4/2009. Read more about this year's final issue here.
- Published:
- 25.11.2009
- Last updated:
- 30.11.2009
