With extreme heat and the worst drought in half a century continuing to plague the farm states, there are important lessons to be learned for all of us -- farmers, consumers and the world's poorest populations alike -- about the effect of climate change.

The Agriculture Department announced this season's first major crop yield forecasts, and they weren't pretty: a nationwide average of 123.4 bushels of corn per acre, the lowest level since 1995. Soybean yield is expected to be low too, though not as bad as corn.

The United States, which is the world's largest producer and exporter of staple grains, is grappling with the biggest surprise in production shortfalls since the Dust Bowl of the 1930s. Certainly, this July surpassed July 1936 as the hottest month on record.

So, how will the devastation affect U.S. crop farmers?

Since mid-June, corn prices have risen about 60%, more than twice the projected decline in yield. This means that farm revenue will go up. About 90% of the corn acreage is backed by a generously subsidized federal insurance program, described by Steven Colbert as "Obamacare for the corn," so crop farmers will be just fine. Livestock farmers who use corn to feed their animals could see higher costs, but most have contracts with processors who provide their feed grains.

What about consumers? Will high commodity prices affect the prices of food you eat? Not much, actually.

Commodity prices account for just a tiny share of retail food prices. If you're a shrewd shopper, next year you may notice higher prices for meat, milk, eggs, and cheese and all types of processed foods. The USDA estimates that food prices will increase 3 to 4% in 2013. This is not going to radically change your life. People in rich countries like the U.S. are not going to eat much less or much differently as a result of modestly higher prices.

The crop losses will have the most effect on the world's poorest populations. About 2 billion people still live on $2 a day or less. Many of them live in urban areas of developing countries. Often, they must spend half or more of their income on food, the bulk coming from staple grains like corn, wheat and rice. For these people, a huge rise in grain prices is more than noticeable -- it can literally break their budget.