So far in this challenge, we haven't talked much about the science of sustainability, in part because you probably already know that to keep our climate stable enough for humans to survive, we need to make some big changes. That's why you signed up.

We are all addicted to coal, oil and gas, and tinkering around the edges isn't going to cut it anymore. The reality is, we need to stop most fossil fuel extraction. And we need to do it in this decade.

If you want to understand the science that explains this horrible fact, you can explore more here and here.

Unless you happen to be a major energy company executive, you may feel like you have no control over whether fossil fuels continue to be pulled out of the ground. But you actually do have some power: your money.

Fossil fuel extraction requires loans from banks. If banks refuse, then the coal, oil and gas stays in the ground. If bank depositors say "we're moving our money to a bank that doesn't fund new drilling/mines/pipelines," banks may listen. And even if they don't, you can sleep a little easier knowing you did your part to try and keep that carbon where it belongs.

The Rainforest Action Network recently updated their report on what banks are financing fossil fuel activity. It includes an easy-to-use bar graph that shows the extent of each bank's involvement in different fossil fuel sectors, and their overall rank.

It's not just the bank where you have a savings or checking account; your credit cards and car loans are funded by a bank, and even your retirement accounts probably include holdings in major banks, as well as in fossil fuel energy companies.

When you start to look, you may be surprised at how many of these banks have some role in your personal finance system. For example, I was disappointed to find out that TD Bank (which issued my Target store credit card) is not only the fifth largest developer of fossil fuels overall, it is a top financer of tar sands extraction. And I had already gotten rid of my Disney credit card a couple years ago, when I realized it was issued by Chase Bank. Sigh.

Pledge to find out what bank is financing at least one of your credit cards or loans, and then investigate if they are a top fossil fuel financer. If you decide to cancel a credit card or move your money to a new bank, be sure to make it known why you are cancelling.

And before opening any new credit, pledge to ask what bank is providing that loan or credit card.

Beyond everyday check writing and credit cards, you can also invest in a fossil-free future!

Fossilfreefunds.org lets you search the funds in your 401K, retirement plan, or personal portfolio and see how much those funds invest in fossil fuel companies. Once you investigate, you can choose investments that focus on companies that promote a green economy, which by the way can make you more money!

The website, run by the non-profit As You Sow, also offers a toolkit to help you discuss your desires with your investment advisor (or with your company's retirement plan to encourage them to offer more sustainable holdings).

You can even look for an investment advisor who can help you make sustainable choices.

"Whatever you do may seem insignificant, but it is most important that you do it.”

― M. Gandhi

Tomorrow we literally put our money where our mouth is...

PS Let us know how we are doing! Email [email protected], or comment on each day's challenge on our website. Thank you!