4.4 Predicting Climate Change

In short, the projections made by climate models have generally been proved correct by real data. Depending on the scenario on which the prediction is based (see below) the outlook is not very good…

The Executive Summary, part of the Introduction to the IPCC Fifth Assessment Report provides a very concise roundup to the predictions, observed recordings and the modelling behind the report. It’s definitely worth a read.

An example of an article in the general Press is here, from the Guardian last July. It discusses the accuracy of climate model predictions and the possible reasons to explain differences in predicted climate and actual climate, when these have been present. It is based upon a paper led by James Risbey in Nature Climate Change, which “takes a clever approach to evaluating how accurate climate model temperature predictions have been while getting around the noise caused by natural cycles”. 

Projections are run for different scenarios for the climate. Each can have a very different outcome. Here are some examples of different scenarios from the IPCC and their predictions for effects on temperature and sea level rise. These are taken from the IPCC Fourth Report in 2007. Each report is based on slightly different data which alters as the technology gets better and more accurate.

Table SPM.3. Projected global average surface warming and sea level rise at the end of the 21st century. {10.5, 10.6, Table 10.7}

	Temperature Change		Sea Level Rise)
	(°C at 2090-2099 relative to 1980-1999)a		(m at 2090-2099 relative to 1980-1999)
Case	Best estimate	Likely range	Model-based range excluding future
			rapid dynamical changes in ice flow
Constant Year 2000 concentrationsb	0.6	0.3 – 0.9	NA
B1 scenario	1.8	1.1 – 2.9	0.18 – 0.38
A1T scenario	2.4	1.4 – 3.8	0.20 – 0.45
B2 scenario	2.4	1.4 – 3.8	0.20 – 0.43
A1B scenario	2.8	1.7 – 4.4	0.21 – 0.48
A2 scenario	3.4	2.0 – 5.4	0.23 – 0.51
A1FI scenario	4.0	2.4 – 6.4	0.26 – 0.59

MULTI-MODEL AVERAGES AND ASSESSED RANGES FOR SURFACE WARMING

Figure SPM.5. Solid lines are multi-model global averages of surface warming (relative to 1980–1999) for the scenarios A2, A1B and B1, shown as continuations of the 20th century simulations. Shading denotes the ±1 standard deviation range of individual model annual averages. The orange line is for the experiment where concentrations were held constant at year 2000 values. The grey bars at right indicate the best estimate (solid line within each bar) and the likely range assessed for the six SRES marker scenarios. The assessment of the best estimate and likely ranges in the grey bars includes the AOGCMs in the left part of the figure, as well as results from a hierarchy of independent models and observational constraints. {Figures 10.4 and 10.29}

Week 3 Reflections

1. What are the most important themes you have learned this week?

This week was in interesting look into the anthropogenic factors affecting climate change. The ratio of the release of CO2 emissions through the burning of fossil fuels compared to deforestation was different to that I expected. 90% through emissions was higher than I thought. I think one of the biggest themes this week was how countries differ in their CO2 production, but how each contribution has an effect globally.

2. What did you find most interesting? And why?

I was interested in the topic of carbon sinks. It brought up questions such as ‘how is the huge amount of carbon being trapped by the ocean affecting it?’ and ‘will there come a point when these sinks are “full” and cannot absorb so much carbon? What then?’ I hope this course will return to these subjects. It’s something I would like to know more about.

3. Was there something that you learned this week that prompted you to do your own research?

A mentioned above, I want to know more about carbon sinks. I will see if they come up in future weeks, but I will be looking into it!

I've just watched the Feedback for this week. Thank you!

3.7 Global carbon emissions

The World Bank publishes a variety of environmental data, including carbon emissions (measured in kt). Create a graph to show a variety of countries at different levels of economic development by following this link to the World Bank web site. Include the USA and China in your graph. Share your graph in the discussion. You may also want to try plot carbon dioxide emissions measured in metric tons per capita. What conclusions can you draw?

This is a fascinating insight into the CO2 emissions globally. I have kept my graph simple for now, looking at some of the major players in the economic and emissions group.

It’s interesting to see how the graph and the picture it portrays changes whether you view the graphs for CO2 emissions per country or per capita.

CO2 emissions (kt)

Data from World Bank

CO2 emissions (metric tons per capita)

Data from World Bank

3.5 Urgent Action

What would you consider the largest threats from extreme weather events to where you live?
The American Geophysical Union (AGU) is a union of scientists dedicated to enhance the understanding of geophysical science.
Follow this link to the latest statement on climate change which was released in August 2013 and is titled Human-induced Climate Change Requires Urgent Action. The statement refers to some of the observations introduced in this week’s lesson including increases in air temperatures, sea level and reductions in Arctic sea-ice. What other examples are included in the statement?
The statement also includes climate projections, which we will introduce next week. Having read the statement what would you consider the largest threats to where you live? Post your responses in the discussion below.

The summary report also mentions the increase in sea temperatures and atmospheric water vapour, the decrease in areas of glaciation, snow cover and permafrost, as well as seemingly counterintuitive changes such as regional cooling. These changes will in turn have an effect on the weather patterns globally.

In the UK we are probably most likely to be affected by a change in seasonal weather patterns. As seen in previous links this week the UK is predicted to have wetter, warmer winters, and possible summer droughts. This would have strong implications on the farming industry of this country. We have seen the effects that such weather has on crops and the country’s infrastructure.

The report mentions that the melting of arctic ice could occur more rapidly than predicted. A rise in sea levels would affect a number of countries, globally, in some cases with devastating consequences. Europe has a lot of low-lying areas which could become affected by this, including the East of the UK.

3.3 State of the climate: extreme events

Follow this link to major climate events created by Climate.gov, then select 2013 and find the nearest major climate event listed to where you are now. Does this provide further evidence of climate change or does it add more complexity to the issue?

The major climate events shown on the map show that in subsequent years there can be a “warmest on record” event, followed by a “coldest on record” one. This shows that there are changes happening. Climate change does not necessarily mean warming of every area on the planet. Changes in weather patterns can affect the climate in a number of ways, some of these having cooling effects.

The example given is the record extent of sea ice in the Antarctic. At first glance this could be taken for good news, it’s not melting! However researchers attribute this to a change in the weather system to the North, which increase the winds across Antarctica. These increase winds actually cool the continent, increasing the sea ice. It is a seemingly counter intuitive result of warming in other regions, showing that climate change works on a global scale, as well as in microclimatic events.

Refs:
http://www.climate.gov/news-features/featured-images/state-climate-extreme-events
http://nsidc.org/news/newsroom/20121002_MinimumPR.html

Week 2 Reflections

1. What are the most important themes you have learned this week?
This week has been an interesting introduction to paleoclimatology. The long-distant changes in the Earth’s climate over its history and how we are able to read these changes in the evidence of rocks, trees and sediments.

2. What did you find most interesting? And why?
I found the idea of the ‘snowball Earth’ fascinating; the feedback mechanisms that can allow such an event to occur, and the processes that reverse it. I found the aspect of there being a ‘tipping point’ of ice cover very interesting, and how that separates this phenomena from an ice age.
I also liked learning about the different methods of being able to ‘read’ the climate history of the Earth.

3. Was there something that you learned this week that prompted you to do your own research?
As discussed in Q2 I found the ‘Snowball Earth’ interesting. The links provided were very useful and yielded an ongoing path to more about the subject.

Week 2. 400ppm

Understanding past climate changes can be key to understanding the state of the climate in the future. On May 9, 2013, carbon dioxide levels in the atmosphere reached the level of 400 parts per million (ppm). The last time the Earth experienced this level of carbon dioxide was in the Pliocene about three to five million years ago. Investigate what the temperatures were during this time period and compare them to today. Using your knowledge from the course so far, what could explain the changes?

During the Pliocene CO2 levels were at a similar level of today. It is thought that a lot of the differences between the Earth then and now were due to the feedback loops discussed last week.

For example, there was significantly less ice both at the poles and on the mountain ranges. This ice albedo loop keeps the temperatures high.

The distribution of heat around the globe was very different. A few degrees shift in temperature has a great effect on the Earth’s oceans and the currents. The change in the sea surface temperature (SST) particularly affected the higher latitudes. These were much warmer than they are today, although the temperatures around the tropics were quite similar.

The comparison with the Pliocene is important because it is one of the few times we can compare climates (then and now) where there are similar taxa living. We can therefore derive some implications for consequences of increasing global temperatures today.