4 ms·

But a lawn fire is not directly temperature related, is it? I suspect the grass has dried from lack of rain, such that some small spark that would ordinarily h

But a lawn fire is not directly temperature related, is it? I suspect the grass has dried from lack of rain, such that some small spark that would ordinarily have fizzled has taken hold.

secretsatan 4y ago
It’s not like it would dry out quicker
maigret 4y ago
The lack of rain comes from the same climate emergency though, this has been confirmed scientifically as well.
- salt-thrower 4y ago
  Not sure why you’re being downvoted. Weather patterns like droughts are exacerbated by climate change. Heat waves are known to make it easier for fires to catch and spread. Heat waves are more common now due to climate change. Thus climate change makes fires more likely/common. It’s pretty straightforward.
  - maigret 4y ago
    Yeah the jet stream is clearly slowing down because the temperature difference with the arctic is lower than before. But to be honest I don’t care much about my karma here. Thanks for the nice answer in any case
    - WalterBright 4y ago
      Please don't care about karma, as catering to it will make your posts less interesting.
  - feet 4y ago
    They're likely getting down voted because climate change deniers want to ignore the evidence that's beginning to scream at us
    - maigret 4y ago
      That’s a good point though. Many tell lobbies are at work, but I think many people can’t take such a harsh change, and I can understand that. We have to focus on changing step by step. The level at which renewables are taking over in many countries is giving me hope.
danans 4y ago
> But a lawn fire is not directly temperature related, is it? The rate of evaporation is directly related to the temperature. Even ignoring additional factors affecting evaporation like wind and topographic variance in dryness, the vapor pressure of water (the biggest contributor to evaporation rate) at 40C is an order of magnitude higher than it is at 20C: https://en.wikipedia.org/wiki/Evaporation#/media/File:Water_vapor_pressure_graph.svg https://en.wikipedia.org/wiki/Evaporation#/media/File:Water_... Sufficient subsequent days of high heat and low humidity will dry out a lawn very quickly, as grass is a plant that is not adapted to retain moisture very well. With hot/dry enough conditions for a sufficient period of time and a bit of kinetic energy in the form of wind, grass that isn't watered quickly becomes flammable, which is why it is usually where large fires first take hold.
quarterdime 4y ago
As a former wildland fire fighter, I can assure you that temperature (and wind and relative humidity) have a HUGE effect on fire behavior. Furthermore temperature and relative humidity (not so much wind) have a huge impact on ignition. My training emphasized this quite heavily, but I thought the effect was exaggerated until I experienced it first hand. In the Western US, construction, mining, forestry, etc. industries are well aware of the fire risk from routine work (construction equipment, off road vehicle traffic, chain saw work, etc.). In "red flag" conditions, there are fire watch policies. For example in forestry work, my crew would have to cease chain saw work late in the morning and stand a fire watch for 30 minutes before leaving the work site. So as I watch the news about these fires, my first thought is ignitions: routine activities (parking a vehicle on grass, driving construction equipment, discarding a cigarette) that would be unlikely to cause a fire in normal (backward looking) UK weather conditions. My next thought is that once a fire has started, it is likely to burn hot and fast. Hotter and faster than I suspect fire fighters in London are accustomed to. As an aside, I have been trying to figure out a good source for weather data. I see plenty of sources for temperature, but I am curious about the wind speeds and relative humidity. From the photos I am seeing, it looks like wind speeds are over 10 mph.
- more_corn 4y ago
  ^ this is why we come to hacker news. Deep contextual comments from knowledgeable professionals. Thank you.
  - russfink 4y ago
    Agreed!
- aeroman 4y ago
  You could try the Met Office website. This is a station in North West London https://www.metoffice.gov.uk/weather/observations/gcpvj0v07 https://www.metoffice.gov.uk/weather/observations/gcpvj0v07 Humidity was about 15-20% during the afternoon, winds 13 gusting 26mph.
  - 4y ago
retard111 4y ago
gdubs 4y ago
If one pours gasoline all over the floor, yes, a match needs to be lit. But the gasoline all over the floor raises the risk of a disaster.
Terretta 4y ago
The ‘lawn fire’ that burned a village today started in a compost heap. Heat was categorically a factor. Together with the heat the compost pile spontaneously ignited. They went to get a hose to douse the smolder, but by the time they got back wind blew embers into dry grass, and woosh. A rare combination of events can cause a compost pile to catch fire. These all must be met before the occasion arises. - The first is dry, unattended material with pockets of debris mixed throughout that aren’t uniform. - Next, the pile must be large and insulated with limited airflow. - And, finally, improper moisture distribution throughout the pile. Key to preventing any issues is proper maintenance of your organic matter to prevent hot compost bins or piles. https://www.gardeningknowhow.com/composting/basics/overheated-compost-piles.htm https://www.gardeningknowhow.com/composting/basics/overheate...

But a lawn fire is not directly temperature related, is it? I suspect the grass has dried from lack of rain, such that some small spark that would ordinarily have fizzled has taken hold.

secretsatan 4y ago

It’s not like it would dry out quicker

maigret 4y ago

The lack of rain comes from the same climate emergency though, this has been confirmed scientifically as well.

salt-thrower 4y ago
Not sure why you’re being downvoted. Weather patterns like droughts are exacerbated by climate change. Heat waves are known to make it easier for fires to catch and spread. Heat waves are more common now due to climate change. Thus climate change makes fires more likely/common. It’s pretty straightforward.
- maigret 4y ago
  Yeah the jet stream is clearly slowing down because the temperature difference with the arctic is lower than before. But to be honest I don’t care much about my karma here. Thanks for the nice answer in any case
  - WalterBright 4y ago
    Please don't care about karma, as catering to it will make your posts less interesting.
- feet 4y ago
  They're likely getting down voted because climate change deniers want to ignore the evidence that's beginning to scream at us
  - maigret 4y ago
    That’s a good point though. Many tell lobbies are at work, but I think many people can’t take such a harsh change, and I can understand that. We have to focus on changing step by step. The level at which renewables are taking over in many countries is giving me hope.

danans 4y ago

> But a lawn fire is not directly temperature related, is it? The rate of evaporation is directly related to the temperature. Even ignoring additional factors affecting evaporation like wind and topographic variance in dryness, the vapor pressure of water (the biggest contributor to evaporation rate) at 40C is an order of magnitude higher than it is at 20C: https://en.wikipedia.org/wiki/Evaporation#/media/File:Water_vapor_pressure_graph.svg https://en.wikipedia.org/wiki/Evaporation#/media/File:Water_... Sufficient subsequent days of high heat and low humidity will dry out a lawn very quickly, as grass is a plant that is not adapted to retain moisture very well. With hot/dry enough conditions for a sufficient period of time and a bit of kinetic energy in the form of wind, grass that isn't watered quickly becomes flammable, which is why it is usually where large fires first take hold.

quarterdime 4y ago

As a former wildland fire fighter, I can assure you that temperature (and wind and relative humidity) have a HUGE effect on fire behavior. Furthermore temperature and relative humidity (not so much wind) have a huge impact on ignition. My training emphasized this quite heavily, but I thought the effect was exaggerated until I experienced it first hand. In the Western US, construction, mining, forestry, etc. industries are well aware of the fire risk from routine work (construction equipment, off road vehicle traffic, chain saw work, etc.). In "red flag" conditions, there are fire watch policies. For example in forestry work, my crew would have to cease chain saw work late in the morning and stand a fire watch for 30 minutes before leaving the work site. So as I watch the news about these fires, my first thought is ignitions: routine activities (parking a vehicle on grass, driving construction equipment, discarding a cigarette) that would be unlikely to cause a fire in normal (backward looking) UK weather conditions. My next thought is that once a fire has started, it is likely to burn hot and fast. Hotter and faster than I suspect fire fighters in London are accustomed to. As an aside, I have been trying to figure out a good source for weather data. I see plenty of sources for temperature, but I am curious about the wind speeds and relative humidity. From the photos I am seeing, it looks like wind speeds are over 10 mph.

more_corn 4y ago
^ this is why we come to hacker news. Deep contextual comments from knowledgeable professionals. Thank you.
- russfink 4y ago
  Agreed!
aeroman 4y ago
You could try the Met Office website. This is a station in North West London https://www.metoffice.gov.uk/weather/observations/gcpvj0v07 https://www.metoffice.gov.uk/weather/observations/gcpvj0v07 Humidity was about 15-20% during the afternoon, winds 13 gusting 26mph.
- 4y ago

retard111 4y ago

gdubs 4y ago

If one pours gasoline all over the floor, yes, a match needs to be lit. But the gasoline all over the floor raises the risk of a disaster.

Terretta 4y ago

The ‘lawn fire’ that burned a village today started in a compost heap. Heat was categorically a factor. Together with the heat the compost pile spontaneously ignited. They went to get a hose to douse the smolder, but by the time they got back wind blew embers into dry grass, and woosh. A rare combination of events can cause a compost pile to catch fire. These all must be met before the occasion arises. - The first is dry, unattended material with pockets of debris mixed throughout that aren’t uniform. - Next, the pile must be large and insulated with limited airflow. - And, finally, improper moisture distribution throughout the pile. Key to preventing any issues is proper maintenance of your organic matter to prevent hot compost bins or piles. https://www.gardeningknowhow.com/composting/basics/overheated-compost-piles.htm https://www.gardeningknowhow.com/composting/basics/overheate...