Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.
![Cloud formation may be linked to cosmic rays - Nature](https://cdn-ak-scissors.b.st-hatena.com/image/square/d30d9b67452bf90270fe2ef4c92619ed83c38a19/height=288;version=1;width=512/https%3A%2F%2Fmedia.springernature.com%2Fm685%2Fspringer-static%2Fimage%2Fart%253A10.1038%252Fnews.2011.504%2FMediaObjects%2F41586_2011_Article_BFnews2011504_Figb_HTML.jpg)