Visualising Global Change

Something a bit different this time, but an interesting perspective on how mass media can change our worldview nonetheless. This week Google Earth updated their Timelapse feature, and it’s really worth checking out (or have a look at the whole collection on youtube here). Not only are the compilations beautiful, they are also an excellent way to visualise the effects we’re having on the planet.

I found the retreat of the Columbia Glacier in Alaska; the cycles of desiccation of Lake Poopó in Bolivia; and rising sea levels in Subarnachar Upazila, Bangladesh three particularly eye-opening and relevant examples. If you’re not convinced by the scale of the problem we’re facing, these might help change your mind. Have a look and let me know what you think.

Arctic Sea Ice

Arctic sea ice isn’t often out the news these days. Whether it’s used by climate scientists as a warning of things to come or by ‘sceptics’ as proof that things aren’t as bad as claimed, it seems the world is very interested on what’s going on up there.

It can be hard to know what to make of all this. One way to visual what’s going on is with Andy Lee Robinson’s 'Arctic Death Spiral'. (Note: many of the graphics this week are from tweets, to ensure their creators are properly credited. This doesn't mean they are poor science though; you can see the source of the data in each of the images. Have a look at those links if you want to find out more!)

#Arctic Death Spiral - October 2016 average vol: 5,539 km³ - 2nd record lowest (last year 7,052 km³, 2012: 5,036 km³) pic.twitter.com/zXmqkYy8dV

— Andy Lee Robinson (@ahaveland) November 14, 2016

Figure 1: The average area covered by sea ice in the Arctic each month since 1979 until October this year.

Each month has its own spiral because the amount of ice in the arctic changes dramatically over the year. As you can see from this graphic, the ice generally peaks around April and is lowest in September, and has dramatically decreased over the last few decades. After September, temperatures drop again and ice begins to form again. Worryingly however, this November has been anomalously warm; up to 20˚C warmer than average for this time of year. This has resulted in a record breaking lack of ice.

Okay, maybe time to let the #Arctic know what season it is -> another drop in #seaice extent from the last 24-hours (3rd day in a row, JAXA) pic.twitter.com/2Fl1pQUsD4

— Zack Labe (@ZLabe) November 20, 2016 

Figure 2: Arctic sea ice extent this month is lower than ever observed at this time of year.

In fact, as of Wednesday, over half the days this year have broken the record for the lowest extent of sea ice for that time of year.

2016 has now broken daily record min Arctic #seaice extent on exactly 50% of days so far this year. Crazy year in the Arctic! pic.twitter.com/crW9rdc3pV

— Zack Labe (@ZLabe) November 23, 2016

Figure 3: This year's Arctic sea ice cover anomaly relative to the previous record minimum for that date.

So what about all those articles asserting that the situation isn’t all that bad? Many are based around overly pessimistic predictions made during the record minimum of 2012 (see figure 4). The absolute minimum has not been this low since, with this year’s September minimum the same as that seen in 2009 (making it the joint second lowest coverage on record). However, although the terrifying event of 2012 is yet to be repeated, as figure 1 shows there is still a very significant decreasing trend. This trend is still outside the worst case scenarios predicted by early models (shown in figure 4). All in all, not all that reassuring, despite what the Daily Mail wants you to think.

Figure 4: Image from Skeptical Science during the record 2012 minimum compared to model projections.

The recent Arctic Resilience Report doesn’t provide much comfort either. It highlights the vulnerability of the Arctic to climate change, and lists 19 tipping points we are approaching there. This video from The Guardian summarises some of the most important (and terrifying) points from the report.

In summary, despite what can be taken away from cherry-picking data or very short term variability, we are seeing a significant and rapid loss of Arctic sea ice. This has the potential to have dramatic knock on consequences on the rest of the world. And if you’re still not convinced of the seriousness of this issue, just remember: no Arctic sea ice= no polar bears. Time to act.

Climate pessimism

This week there has been a lot of pessimism regarding climate change in the news, largely due to the result of a certain election. For the sake of my sanity we are not going to dwell on said result, but instead look at a different gloomy story in the news this week. The Independent summed up the media stories well with this headline: ‘Climate change may be escalating so fast it could be 'game over', scientists warn. New research suggests that the Earth’s climate could be more sensitive to greenhouse gases than previously thought, raising the spectre of an ‘apocalyptic side of bad’ temperate rise of more than 7C within a lifetime’.

So are scientists actually warning this? The news articles are based on a paper published in Science Advances this week. The scientists in question were aiming to test current projections of how the Earth’s climate system will respond to increasing CO₂ using data about past climates.

They reconstructed a global surface air temperature record for the last 784,000 years, using sea surface temperature proxies from across the world. They then correlated this to records of atmospheric CO₂ (from air bubbles trapped in ice sheets), and used this to assess the sensitivity of the Earth’s climate system to changing CO₂ levels.

Box 1- SST proxies On much of the ocean floor sediment builds up gradually and constantly over time. This sediment often contains indicators of conditions at the time it was deposited- a climate proxy. A commonly used example (including in this paper) is the calcite shells of microorganisms called foraminifera. Depending on the species, the chemical and physical make up of the shell can give us a lot of information about the climate and water the shell formed in. The ratio of different oxygen isotopes (commonly written as δ18O) can give information about temperature and ice volumes at the time, as can other relationships such as the ratio of calcium to magnesium or the direction the shell coils in. By taking cores of sediment containing these proxies, scientists can reconstruct an accurate picture of how climate changed over the period the sediment was being deposited. Henderson (2002) provides a more detailed discussion of a number of proxies if you’re interested in learning more.

They found that there results were generally in good agreement with the projections they looked at. These were from CMIP5 (the coupled model inter-comparison project 5) which provided the projections used in the 5^th IPCC report  (see previous blog post) . It’s worth noting that all projections come with significant uncertainty- we don’t really know how things like cloud formation will feedback into climate responses. This is why when you see projections on graphs there is not a thin line, but a thicker band. The results from this study are well within the CMIP5 uncertainty range, but the maximum emissions scenario shows temperature increases by 2100 around 16% higher than the mean of the projection.

Figure 1: CMIP5 projections based on different emissions scenarios (here called RCPs). RCP8.5 is the projection referred to in this paper.

This is where the headlines come from. The study found that as the climate warms it becomes more sensitive to CO₂ i.e. that there is more warming per unit of CO₂. This might put the Earth at risk of ‘runaway’ climate change- where positive feedbacks amplify warming and the system spirals out of control. 7˚C would indeed be catastrophic, but these projections are based on high emissions scenarios where we do nothing to reduce how much CO₂ we produce. If we stick to our 2˚C ambitions we stand a good chance of avoiding runaway change.

One criticism of this paper is that over the period studied CO₂ levels have never been as high as they are today, never mind how high they would be in the worst case scenarios referred to in the headlines. They therefore cannot test climate responses to the type of climate forcing expected later this century. However, this paper finds good agreement with previous studies looking at longer time periods in which CO₂ was higher, for example Köhler et al (2015), who looked the last 5 million years.

So the two main takeaways from this post (apart from never trust a headline) are:

1.       There is more and more evidence that in the past climate responded to increasing CO₂ in a similar way to the way CMIP5 models suggest it will in the future. This means we have more confidence in the projections in the IPCC report for example. So if we stick to the 2˚C pathway we're in for a decent shot of avoiding the apocalypse.

2.       The warmer the world gets, the greater the effect additional CO₂ emissions will have on climate, and the more uncertain we are about its impacts. The more we emit, the higher the risk that the climate system spirals out of control. Even more of a reason to cut emissions fast!

Let’s hope the world’s leaders are ready to take bold actions to save the planet. Oh wait...

COP21

In December 2015, leaders from across the globe met in Paris at the UNFCCC’s (United Nations Framework Convention on Climate Change) COP21 conference in Paris. 197 countries signed a historic agreement committing, for the first time, to limit total global temperature increases to ‘well below’ 2˚C above pre-industrial levels. It was also recognised that a target of 1.5˚C would be more desirable. The Paris Agreement  is the the topic of this blog post because today it entered into force. This means that countries which have ratified the treaty (a total of 97 counties responsible for 66% of global emissions) are now legally bound to it.

This is certainly a big step forward, and when the agreement was signed in December, and again today on its implementation, there were a swath of celebratory headlines. For example, both CNN and The Guardian published articles labelling it ‘the end of fossil fuels’. Others however were critical.

So what’s the true story? Admittedly, amongst the hysteria there were a number of articles that were balanced and accurate. However, I think the best analysis is in the UNEP (United Nations Environment Program) Emissions Gap Report, the launch of which I was lucky enough to attend yesterday. The report looks at whether countries are sticking to previous climate commitments, such as Cancun 2020 pledges, and what impact the Paris Agreement may have. It’s a very interesting read, and I’d really recommend having a look using the link above. 

In short, it identifies a significant gap (hence the name) between current pledges and actions and those needed by 2030 to keep us on track for the 2˚C goal. According to their analyses, annual emissions will need to be reduced to 42 Gt CO₂ (1 gigatonne (Gt) = a billion tonnes) by 2030 to have a 66% chance of meeting our 2˚C target. Based on the pledges made at Paris (see Box 1) we are projected to be 12-14 Gt above this. This would result in a temperature increase of 3.4-3.7˚C.

Box 1: INDCs After the failure of the 2009 Copenhagen summit due to countries being able to agree how to split the responsibility for reducing emissions, a new approach was sought. Each country came to Paris having decided their own emissions reductions pledges, or ‘Intended Nationally Determined Contributions’ (INDCs). This did resulting in successfully reaching the groundbreaking agreement to limit warming to 2˚C, but the total of the INDCs is not sufficient to get there. Furthermore, some INDCs were conditional, for example on financial aid.

Image 1: Projected possible emissions pathways, based on business as usual, current policy, and Paris pledges scenarios. Image taken from the UNEP Emissions Gap Report.

Overall then, the Paris Agreement shows governments across the globe are taking the threat of climate change seriously and are willing to take serious steps to combat it. It also shows the potential for global diplomacy, and is a cause for optimism in this sense. However, it does not represent a ‘solution’ to climate change. We are still a long way off a point where global leaders reach an agreement that will actually achieve the aim they signed up to Paris.