Heavy rains have been reported in Kalimantan starting October 26 and since then the fire season has been coming to an end. There are still fires burning but nothing compared to those that burned earlier in the season.
This figure shows how the current fire season progressed in relation to previous ones (2003-2014). On October 21 this year passed 2006, which was the highest fire year in the MODIS satellite era, 2000 onwards. The main fire season is August through October when the southern part of Indonesia experiences its dry season. However, in some years including 2014 the fire season in the northern part of Sumatra is prominent as well, burning in February and March.
We expect that the GFED estimate for the 2015 fires will be about 1.75 billion metric ton of CO2 equivalents, with substantial uncertainty.
Above the greenhouse gas emissions from Indonesian fires are plotted according to GFED for 1997-2014 with estimates for 2015 based on active fires. These are converted to emissions based on a relation between the two, established using data from previous years, see the figure and text below for more information. The numbers on the right indicate fossil fuel CO2 emissions for various countries for 2013 derived from the EDGAR database.
In general, fire CO2 emissions are compensated for by regrowing vegetation after a fire and should not be compared to fossil fuel emissions, but that is not the case when forests are burned to make way for other land uses or when peat is burned. That is exactly what happens with the vast majority of the fires in Indonesia and these fires are thus a net source of CO2 as well as other greenhouse gases.
Conversion of active fires to emissions
This graph shows how we derive the 2015 estimates. The grey dots indicate the total annual active fire observations in Indonesia on the horizontal axis and the corresponding GFED estimates are on the vertical axis with the years 2006 and 2014 labeled. Each grey dot represents one year between 2003 and 2014. The relation is not perfect and adds some uncertainty to those that are in these estimates already. The non-linearity is probably related to smoke obscuration of active fires in high fire years.
Note: we have adjusted the trendline describing the relation between active fire detections and emissions on October 20 to better represent the high fire years, especially 2006. This led to a small increase in emissions compared to the relation used before October 20.
Using the conversion from active fires to emissions we can calculate daily emissions which is shown above. This has generated a lot of media interest after WRI showed that on many days the rate exeeds that of fossil fuel emissions in the US (roughly 15 million ton CO2 per day). Keep in mind though that these fires do not burn continuously at this rate: on a global annual scale they are far less important for climate change than other sources of greenhouse gases.
A few things to consider:
- These estimates contain a substantial amount of uncertainty related to the complex fire situation in Indonesia. We would very much welcome opportunities to lower uncertainties which is poorly supported by the regular national agencies.
- Top-down studies using atmospheric observation provide some confidence in the emission estimates provide here, see for example Aouizerats et al. (2014) and Van der Werf et al. (2009)
- GFED starts in 1997, there is information on earlier years thanks to work of, amongst others, Wooster et al. (2012) and Field et al. (2009). That work supports the tight link between (El Nino related) drought and fires. However, El Nino is not the root cause: the work of Field shows that without humans these extreme fire seasons would not exist.
- In addition to greenhouse gas emissions from fires, drainage of peatlands also leads to CO2 emissions from decomposition. The emissions are not as visible as those from fires but may be of similar magnitude according to the work of Hooijer et al. (2010), although not as variable from year to year.
For more information please contact Guido van der Werf