Angel Hsu, postdoctoral associate at Yale University
"The increased in extreme weather events is of particular concern to China, which has a high proportion (~26.6%) of urban residents living in low-elevation coastal cities, compared to other countries, according to a study by Balk et al. (2011). These low-lying coastal areas are especially vulnerable to such events and are already happening in major cities in China, such as Beijing, which experienced the heaviest rain in nearly six decades and saw at least a dozen people dead or injured in the summer of 2012.
Another major conclusion from the IPCC Fifth Assessment WG1 that has ramifications for China is in the discussion of the ‘global carbon budget’ and how quickly it’s being spent. New scientific evidence that suggests that the cumulative amount of carbon dioxide (CO2) emissions, rather than the timing of their release that is more closely related to warming temperatures. Therefore, conversations of ‘peak emissions’ or when China’s emissions are expected to reach their zenith before decreasing, may not be as relevant if considerations of the carbon budget are not taken into account.
As China is the largest emitter of carbon dioxide (CO2) emissions and is expected to maintain this number one spot for several more years, international pressure could mount for China to adopt more drastic cuts in CO2 prior to its expected peak year (estimated to be 2030, although newer studies suggest that with market mechanisms this date could be pushed forward several years)."
Li Shuo, campaigner at Greenpeace
"One thing that stands out is that climate change is not always linear. There are a number of components in the climate system that may change abruptly and perhaps irreversibly, once they cross a certain threshold, causing substantial disruptions to people and natural systems. For example, scientists have been warning about potential methane bombs from clathrates, collapsing ice sheets and dying tropical forests, among other things. But it’s inconvenient how little we still know about these threats.
The only insurance policy against abrupt changes is to cut emissions as fast as possible, to limit further warming.
On the issue of future sea-level rises, the scale will depend on how fast we cut emissions and whether we manage to avoid triggering a near-complete loss of the Greenland Ice Sheet. Knowing how dependent we are on coastal regions, keeping sea-level rise as low as possible should rank very high in our list of priorities.
Since 1901, global mean sea level has risen by about 19 cm. The mean rate was about 1.7 mm per year, but between 1993 and 2010 the speed was almost double (3.2 mm / year). During this century the rate will exceed that observed during 1971–2010, even if rapid emission cuts were implemented.
The effects of mean sea level rise will be felt most acutely during extreme sea level events such as storm surges due to severe weather events. It is very likely that there will be a significant increase in the occurrence of future sea level extremes by 2050.
It is not only small island states that need to worry about sea level rise. Sea level rise increases the risk of both temporary and permanent flooding of coastal lands. Around 23% of the worlds’ population lives in the near coastal zone with population densities about three times higher than the global average. Of the 39 big metropolitan areas with a population over 5 million, 60% are located within 100km of the coast. These include twelve of the biggest 16 with populations exceeding 10 million although the great majority of people live in smaller settlements in the coastal zone.
With a one metre sea level rise some island nations, such as the Maldives, would be submerged. Already, two of the islands that make up Kiribati (a Pacific island nation) have gone under the waves, and in early 2005 others were inundated by a high spring tide that washed away farmland, contaminated wells with salt water, and flooded homes and a hospital."
Wu Changhua, China director at The Climate Group
“The increase in certainty obviously further underpins the scientific understanding of and confidence in the causes of climate change. In practical terms however, it doesn’t really change the case for action, which has been overwhelmingly clear since the last IPCC Assessment Report in 2007 and indeed earlier. Today, we just have a bit more certainty about a problem, which we were already highly certain of.
The issue of climate sensitivity is definitely an important debate as it will calibrate the policy responses of governments. That said, the reduction in the climate sensitivity range looks likely to apply mainly to upper temperature extremes. The new ranges that scientists have mentioned still cover a spread of temperatures (eg 2-4.5C, I believe) that would have very serious, indeed disastrous, consequences for countries and economies, as major institutions, such as the World Bank, have pointed out. To suggest that everything is ok and that we don’t have to worry about rising levels of emissions because of reduced climate sensitivity, as some skeptics have argued, is just plain wrong. The risk of dangerous climate change remains and a prudent, pragmatic response is to take immediate action to mitigate emissions in order to avoid costly and damaging impacts.
Sea levels have already risen by approximately 20cm over the last 150 years or more according to the last IPCC report (2007), driven mainly by the expansion of water as it has warmed. The rate of increase has accelerated in recent decades, with scientists attributing this to an increasing loss of ice and snow from land-based glaciers and icesheets (NB: sea ice loss does not contribute to sea level rise). The main risk right now is how this increase is exacerbating natural phenomena such as coastal erosion and ‘king tides’, which obviously have serious implications for low lying areas, not least small island nations.
In terms of China, it is one of the most vulnerable countries to climate change in recent decades. Sea level rise along the coast has been witnessed higher than global average; more severe and frequent extreme weather, especially floods and droughts, have been impacting larger regions and regions that had never experienced this level of impact before. As a result, the already vulnerable water security – featured as “too much, too little and too dirty” – poses a larger risk to the country’s economic growth and quality of life. With a few percentage points of annual GDP wiped out by extreme weather, China has to think really seriously about how to increase its resilience to climate change."
Martin Bunzl, founder of the Rutgers Initiative on Climate and Society
"Consider the following question, whether you have read the new IPCC report or not. “What could it tell us, that would make a difference?” My answer is, “not much”.
Nor do I think any future IPCC report could either. I say this because after five reports, we are now in the phase of refinement of past findings. The knowns are becoming a little more known and the unkowns a little less unknown. But there are not going to be any dramatic changes in the findings.
Whether by deliberate choice (to avoid making hard choices) or not, by allowing climate policy to be a slave to climate science, we allow the natural caution of scientific claims to infect rational choice when it comes to policy. That is especially true when it comes to the question of climate sensitivity, especially the further out we go in time and ppm levels of greenhouse gasses.
The new report drops the bottom of the likely range from 2.0C to 1.5C but holds the likely upper limit the same at 4.0C as compared to the previous report. These are projections based on a doubling of pre-industrial levels of carbon dioxide. But of course, even if they are right, if we carry on with business as usual, the idea that we will limit output to (roughly) 540 ppm is absurd. And thus the associated temperature ranges will be much much higher.
Be that as it may, how much confidence should we have in these projections? This question is misplaced. From a policy point of view it ought not to matter. Hard choices about policy always occur in the context of uncertainty.
You don’t need to know smoking causes cancer for sure to give up smoking. It is enough that there is a risk of it doing so given the cost if it in fact does do so. In technical lingo, if the expected disutility of the outcome is high enough, as long as the probability of the outcome is above zero, it is worth avoiding the risk.
And as with individual choice under uncertainty, so to with social choices as well."
Mike Hulme, professor of climate and culture, Kings College London
“This must surely be the last IPCC report in its current form. It takes too much effort, by too many scientists, over too long a time period, to produce too long a report (2000 pages), which doesn’t really help climate policy-making in any substantive way. I have argued for a while now that there should be much shorter, quicker, more focused reports on specific aspects of climate science—and then, separately, assessments for major world regions written by diverse stakeholders and experts exploring what a changing climate means for adaptation, energy and development. These don’t all have to be owned by the IPCC.
On the one hand this IPCC report claims that scientists are more certain that humans are having a major influence on the climate system—we’ve known this for a while!—but on the other hand the report makes clear that there is a lot we still don’t understand about how the climate system will warm in the future (this is the climate sensitivity problem), nor how regional rainfall patterns, storms, etc., will change. Here, significant uncertainties remain. As with much complex science, more research leads to more questions; for every question in IPCC AR4 that has been answered, two new questions have emerged. This is the nature of science.
What the hiatus in global temperature since the 1990s has told scientists—and many have been surprised by this hiatus—is that it is good and proper to ask critical questions about the state of climate knowledge. Science never produces finished products, only provisional ones. But being sceptical about climate science does not automatically entitle one to be negative about climate policies—the question is what sorts of climate policies are most appropriate—effective and plausible—given what we know today. The problems of energy supply, weather risks and poor air quality all need to be tackled in some way even if the climate sensitivity was only 1.5C.
This latest assessment of climate science from the IPCC threatens to distract from resolving the core issue of climate change – the political challenge of finding policy interventions that are effective and plausible. The difficulties in implementing policies that reduce the dangers of a changing climate don’t result from a deficiency of scientific knowledge. Raising the confidence that humans are a major influence on climate from ‘very likely’ to ‘extremely likely’ doesn’t change the politics of climate change. The difficulties arise because of different interests, values and attitudes to risk. These can only be worked through using political strategies that are less constrained by the need to reach global agreements.
We need a more pragmatic politics of climate change, not more weighty science about climate change.”
