Major update of content for the home page.

Didier BARRET
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content.yml
@@ -319,158 +319,63 @@ home:
       - title: What does the tool do?
         content: |
-          The tool computes the travel carbon footprint associated with round trip flights. It does so for a set of trips from a given city of origin to a set of destinations. Similarly, the tool allows to compute the carbon travel footprint of a larger set of trips, corresponding to a conference, a meeting. For this, the city of departure for each participant to the conference has to be provided. If multiple host cities are provided, the tool ranks the cities according to the associated carbon footprint. While online calculators enable to compute the footprint of a limited number of trips, this tool enables to compute the footprint of a larger number of trips in an automated way. Furthermore, it provides an estimate based on data from six different methods, whose estimates can differ significantly. If more than one method is selected by the user, the tool returns the mean of the estimates of each method.  
-          
-          <!--
-          For short distance travels, the CO<sub>2</sub> footprint associated with trains
-          is calculated and added to the air travel footprint.
-          -->
-
-          ### Original Motivation
-
-          Global warming is a threat for life on our planet. Evry day we hear about 
-          scientific results demonstrating the devastating impacts this will have on
-          Earth in the very near future.
-          Emissions of carbon dioxide by aircraft were 0.14 Gt C/year in 1992.
-          This was between 2% of total anthropogenic carbon dioxide emissions in 1992
-          or about 13% of carbon dioxide emissions from all transportation sources
-          (Intergovernmental panel on climate change, report 1999). Due to an 
-          increasing demand and the growth of the world economy,
-          the number has grown since then, reaching closer to 3% nowadays,
-          a number which will keep growing.
+          The tool computes the carbon footprint associated with round trip flights. It does so for a set of trips from a given city of origin to a set of destinations. Similarly, the tool allows to compute the carbon footprint of a larger set of trips, corresponding to a conference, a meeting and so on. For this, the city of departure for each participant to the conference has to be provided. If multiple host cities are provided, the tool ranks the cities according to the associated carbon footprint. While online calculators enable to compute the footprint of a limited number of trips, this tool enables to compute the footprint of a larger number of trips in an automated way. Furthermore, it provides an estimate based on data from six different methods, whose estimates can differ significantly. If more than one method is selected by the user, the tool returns the mean of the estimates of all selected method.
-          Carrying scientific research requires traveling all across the world,
-          but time has come to critically look at the way we carry research,
-          with the aim of raising awareness and reducing our environmental impact,
-          whenever possible. As air travel is likely to dominate the CO<sub>2</sub> budget
-          of most scientists, this tool offers a way to easily compute the footprint 
-          associated with travels. 
-
-      - title: Which data are used?
+      - title: How does the tool work?
         content: |
-          There is a growing interest in getting the travel footprint of scientific events,
-          such as conferences or large meetings.
-
-          Those are based on freely available CO<sub>2</sub> calculators,
-          some being relatively easy to use, requiring very limited user inputs.
-
-          However, just by running some of them (including those from Carbon offset companies),
-          it is amazing to see how their estimates can differ quite significantly
-          (up to a factor of a few for the same trip).
-
-          This is because they use different input data and consider different perimeters and assumptions,
-          e.g. excluding freight or not, assuming different radiative forcing indices,
-          seat accommodation in the plane…
-
-          The straight numbers provided should therefore not be taken at face value,
-          but should be looked at, for what they include and mean.
-          It is also striking to me that there is hardly any scientific literature
-          on the comparison between CO<sub>2</sub> calculators,
-          although often discrepancies are noticed in some communications,
-          more particularly for long distance flights.
-
-          Relying on one calculator is therefore not possible. This tool thus 
-          enables to compute your travel carbon footprint (for round trips),
-          based on data provided by 6 independent calculators:
-
-          1. the International Civil Aviation Organization (ICAO),
-          2. the UK Department for Environment, Food & Rural Affairs (DEFRA),
-          3. the ATMOSFAIR German Carbon offsetting company,
-          4. the French Environment & Energy Management Agency (ADEME)
-          5. the data provided on the KLM website to introduce their CO2 compensation service (KLM)
-          6. the MyClimate Carbon offseting company (used by Lufthansa)
-
-          ICAO, DEFRA, MyClimate, ATMOSFAIR and to some extent KLM have 
-          their methodology very well described
-          (see resources section below).
+          A round trip is defined by a city pair. The two cities are geolocated and from their longitude and latitude, the great circle distance is computed. This is the shortest path a plane can follow. Some methods thus consider uplift correction factors in computing the carbon dioxide emission of a flight. In addition, two cities may not be connected by a direct flight. This is accounted for by increasing by 5% the great circle distance. Each method provides the carbon dioxide emission in kg as a function of the flight distance in km. Thus from the increased great circle distance, the carbon dioxide emission of a flight associated with a trip between a city pair is computed and multiplied by two to account for a round trip. 
-          ADEME and DEFRA provide mean emission factors.
-          ATMOSFAIR and ICAO provide on line emission calculators requiring limited user inputs.
-          Those on-line calculators have been run for a variety of flight distances,
-          so that the estimates (without error bars) could be approximated with linear functions.
-
-      - title: How does this tool work?
+      - title: Which methods are used? 
         content: |
-          The tool starts by decoding the origin cities listed in the form, and geolocate them. 
-          It then decodes the destination cities and geolocate them as well. 
-          
-          Cities that cannot be located are ignored from the computation. To resolve ambiguity 
-          between cities of similar names (e.g. Cambridge), the name of the country is required.
+          The tool incorporates six different methods, among the most widely used, and for which the methodology used is documented. Providing more than one method enables to get a mean value, while illustrating the significant differences in their estimates. In alphabetic order, the data considered are from ADEME: the French Environment & Energy Management Agency, atmosfair: a German carbon offsetting company, DEFRA: the UK Department for Environment, Food & Rural Affairs, ICAO: International Civil Aviation Organization and finally from the KLM carbon compensation service. This list is obviously not exhaustive but represents a variety of estimates from lower to higher values. 
-          From the longitude and lattitude of the origin and destination cities, the great 
-          circle distance is computed. This is the shortest path a plane can follow. However,
-          traveling between cities often involves connexion. A 5% increase of the great circle 
-          distance is considered as a mean value.
+      - title: How are the different methods built? 
+        content: |
+          What is needed for each method is a function giving the carbon dioxide emission as a function of the flight distance. ADEME and DEFRA provide mean emission factors, as a function of flight distance. Myclimate provides an analytical formula. For ICAO and atmosfair, the on-line calculators have been run for a wide range of flights of varying distances (~100 flights spanning from 300 km to 12000 km) and the estimates have been fitted with linear functions, covering adjacent distance intervals. For its carbon compensation service, KLM provides on its web site a table of emissions for a large range of flights. The KLM data have been also been fitted with linear functions. 
-          DEFRA, ICAO, Atmosfair and MyClimate include uplift factors to account for the fact 
-          than planes, even during direct flight, do not strictly follow the shortest path,
-          e.g. to avoid bad weather conditions. For instance, MyClimate considers what is 
-          called a detour constant of 95 km.
-
-          CO<sub>2</sub> emissions per passenger take into consideration the load factor
-          and are based only on passenger operations
-          (i.e. fuel burn associated with belly freight is not charged to the passenger).
-          From the travel distance, and the emission coefficients, the tool computes the amount
-          of  CO<sub>2eq</sub> generated by each flight. The user can select one 
-          or more methods, and a mean value will be reported if more than one method is considered. 
-
-
-    # Second row of "blocks"
-    - blocks:
-
-      - content: |
-          ### What about Radiative Forcing? {#rfi}
-          CO<sub>2</sub> emissions is computed from the total fuel burnt during the flight.
-          For ICAO one kilogram of fuel leads to **3.16** kg of CO<sub>2</sub> emissions.
-          MyClimate instead considers the same emission factor but adds a 
-          factor for pre-production of 0.538 kg CO<sub>2</sub>e/kg jet fuel (ecoinvent 2018).
-        
-          Radiative forcing accounts for the fact that aviation contributes to climate change
-          more than just with the emission of CO<sub>2</sub> from burning fuels,
-          by releasing gases and particles directly into the upper troposphere
-          and lower stratosphere where they have an impact on atmospheric composition.
-          These gases and particles include carbon dioxide (CO<sub>2</sub>),
-          ozone (O<sub>3</sub>), and methane (CH<sub>4</sub>);
-          trigger formation of condensation trails (contrails);
-          and may increase cirrus cloudiness;
-          all of which contribute to climate change.
-          A radiative forcing index of 1.9–2 is recommended by DEFRA, MyClimate and ADEME.
-          ATMOSFAIR considers a multiplier of 3, for all emissions above 9 km.
-          ICAO, on the other hand does not include a multiplier,
-          waiting for the scientific community to settle on a value.
-          KLM data do not account for radiative forcing either.
-
-      - title: Which seat category are you considering?
+      - title: What about radiative forcing? {#rfi}
         content: |
-          The tool considers only economy seats for the time being.
-          Note that DEFRA emission factors are a factor of 3 larger for a business class seat
-          (proportional to the larger area used in the plane).
-          Similarly, a factor of 1.5 should be considered when flying on Premium economy seats
-          (ICAO would consider a factor of 2).
+          Radiative forcing accounts for the fact that aviation contributes to climate change more than just with the emission of carbon dioxide from burning fuels, by releasing gases and particles directly into the upper troposphere and lower stratosphere where they have an impact on atmospheric composition. These gases and particles include carbon dioxide (CO2), ozone (O3), and methane (CH4); trigger formation of condensation trails (contrails); and may increase cirrus cloudiness; all of which contribute to climate change. A Radiative Forcing Index (RFI) of 1.9–2 is used by DEFRA, myclimate and recommended by ADEME (see discussion in Jungbluth, N. & Meili, C. Int J Life Cycle Assess (2019) 24: 404. https://doi.org/10.1007/s11367-018-1556-3). ATMOSFAIR considers a multiplier of 3, for all emissions above 9 km, accounting for the profile of the flight. ICAO, on the other hand does not include a multiplier, arguing that the scientific community has not settle on a value! KLM data does not seem to account for radiative forcing either, as the estimates they provide are close, although a little higher, than the ones of ICAO. Therefore, the methods based on ICAO and KLM data are not recommended, but given as methods providing the lowest emissions. 
-      - title: What about uncertainties?
+      - title: Original motivation
         content: |
-          Each estimate may have an uncertainty between 10 and 25%
-          (really this is a best guess, and not substantiated by any statistical 
-          analysis and it could be more probably).
-          We would therefore refrain from using the numbers derived as absolute values.
-          Larger differences are found when long distance flights are considered.
-          In all cases, the estimates can be used for relative comparisons.
+          Global warming is a threat for life on our planet. Emissions of carbon dioxide by aircrafts keeps increasing, as the world economy keeps growing (it is about 3% of the anthropogenic emissions nowadays). Carrying scientific research requires traveling across the world, and thus air travel is likely to dominate the carbon footprint of most scientists. This tool was first developed to enable each scientist to easily access its travel footprint. It was then used to compute the travel footprint associated with the development of a large international project, such as the Athena X-ray Integral Field Unit. The numbers were then used to propose concrete actions to reduce the footprint of the project, by reducing the number of large meeting, implementing different ways of interacting and working collectively in a world-wide consortium. Finally, by comparing different, widely used methods, providing so different estimates, the tool is expected to raise awareness within the scientific community (and hopefully the authorities) about the lack of regulations or framework on the critical matter of flight emissions.
-    # Third row, etc.
     - blocks:
-      - title: Considering train travel for short travel distance
+          
+      - title: Seating category
         content: |
-          There is a minimum distance (by default 300 km)
-          under which the calculator excludes flight travel.
-          The calculator proposes instead to compute the travel footprint associated with train.
-          The French emission factors are between 4 and 5 grams of CO2eq per km per passenger.
-          This low value is likely due to the fact that electricity is provided by nuclear plants.
-          It is larger by some factor accross Europe.
-          Here I am assuming that the French factor are multiplied by a factor of 5.
-          This makes train typically 10% less emitting than plane (including radiative forcing).
-
+          The tool assumes economy seats in computing the carbon dioxide emission. For indication, DEFRA provides mean emission factors for different seat classes considering international flights. Related to the area occupied by the seat in the plane, for Premium economy, the emission would be 1.6 times larger than flying an economy seat. It would be 2.9 and 4 times higher from flying Business class and First class respectively. 
+          
+      - title: Accounting for train emission
+        content: |
+          The minimum distance for flying is considered arbitrarily to be 300 km. Below that, it is assumed that train is used. The tool then computes the travel footprint associated with train. The French emission factors provided by ADEME are 3.37 and 5.11 grams of carbon dioxide equivalent per km per passenger for high speed train and normal train respectively. This low value is due to the fact that electricity is provided by nuclear plants. It is larger by some factor across Europe. The tool assumes the mean of the emission factors of national and international rails, as provided by DEFRA (i.e. 23 grams per passenger km). This makes the carbon dioxide emission of trains, typically one tenth (1/10) of the one of aircrafts.
+          
+      - title: Input and output data and trouble shooting
+        content: |
+          The inputs are provided in US English for the city and country names, without diacritics. On each line, the city and country names must be separated by a comma.  The estimation can go wrong if a city is not properly geolocated. This may happen because the name of the city is wrongly spelled, or the geolocator (OSM) is confused or unavailable. An error should be listed at the end of the result page. Don’t be surprised, if the name recovered by the geolocator is not exactly the one you had expected. The result pages provides a summary plot which can be downloaded, as well as a csv and raw yaml file. The csv file lists the name of the city as in the form, the address to which it was geolocated, the carbon dioxide emission (in kg), the distance travelled, the number of trips possible by train (i.e. when the distance is less than the minimum flying distance, e.g. 300 km) and the number of trips by plane. The plot and the csv file rank the city against the carbon dioxide emissions. Cities found identical in the input form are grouped, and their number in the group is given by the number of trips, and the distance given is the cumulative distance over the group.
+          
+      - title: Caveats
+        content: |
+          The numbers provided by the tool do not come with uncertainties. Therefore they must be considered as indicative of the true values. Selecting more than one method is recommended. In all cases however, the numbers can be used for relative comparisons, e.g. when comparing two cities for hosting a conference. 
+          
+      - title: Confidentiality
+        content: |
+          The data provided in the form will remain confidential, as will be the results.
+          
+      - title: Disclaimer
+        content: |
+          This tool is provided on a best effort basis as a service to members of the science community. The numbers provided are informative and have obviously no legal value. 
+          
+      - title: Reference
+        content: |
+          Results from the tool may reference to Barret (2019, in preparatiion). 
+ 
+      - title: Concluding note
+        content: |
+          As a personal note, I would like to stress that, as a scientist, I find it worrying or even shocking that there are no standards for computing the flight emissions, while we know that flight travels, releasing carbon dioxide at high altitudes, contribute to global warming. To take an example, the International Civil Aviation Organization (ICAO) is a United Nations specialized agency, established by States in 1944 to manage the administration and governance of the Convention on International Civil Aviation. ICAO has global responsibility for the establishment of standards, recommended practices, and guidance on various aspects of international civil aviation, including environmental protection. How can ICAO ignore radiative forcing in the results provided by its widely used on-line calculator? (which by the way is the calculator used by the travel agency of my institute, being a public institution). The IPCC in its 1999 report have defined the radiative forcing index to be between 2 and 4. Why ICAO is using 1? This is just an example, which clearly show the urgent need to agree on a common methodology accepted by all parties in computing flight emission. May this tool be used for that purpose. 
+          
       - title: Additional resources
         content: |
           - Offset your flight with [atmosfair](https://www.atmosfair.de/en/offset/flight)
@@ -489,23 +394,6 @@ home:
           - L. Hackel [travel footprint calculator](https://lhackel.shinyapps.io/travel_footprint/)
             based on DEFRA emission factors
-      - content: |
-          ### Disclaimer
-
-          This tool is provided on a best effort basis as a service to members of the science community
-          to get some ideas of travel footprints associated with scientific projects and activities.
-
-          ### Confidentiality
-
-          The data provided will remain confidential, as will be the results.
-
-          ### Troubleshooting
-         
-          The estimation can go wrong if a city is not properly geolocated.
-          This may happen because the name of the city is wrongly spelled,
-          or the geolocator (<acronym title="Open Street Map">OSM</acronym>)
-          is confused or unavailable.
-          An error should be listed at the end of the result page.
 estimate:
@@ -598,4 +486,4 @@ estimation:
 footer:
   credits: |
-    Didier Barret © 2019
+    Didier Barret (IRAP) © 2019