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updated 5/15/2012 2:25:35 PM ET 2012-05-15T18:25:35

Last month's temperatures sustained the trend of unusually warm weather so far this year for most of the United States, bringing the third warmest April on record to the lower 48 states. Across the globe, April was the fifth warmest on record.

Both records, kept by the National Oceanic and Atmospheric Administration (NOAA), date back to the late 19th century.

This follows the warmest March on record in the lower 48 states since record keeping began in 1895, as well as above-average, though not quite as remarkable, global temperatures. The first four months of 2012 brought the fourth warmest winter on record to the lower 48 states, according to NOAA.

Of course, these temperature records are averages, so some places saw cool temperatures.

Norway and Sweden, for example, saw their coolest April since 1998.

The unusual warmth in many places, particulary Russia, the United States including Alaska, and parts of the Middle East and western Europe, may immediately bring to mind global warming; however, scientists who study climate avoid blaming human-caused climate change for short-term fluctuations in weather, because weather fluctuates from day to day and season to season. The effects of climate change become apparent only over the long term.

However, the warmth isn't unexpected. Records like NOAA's make it clear the world is warming up. For instance, the last decade that began in 2000 was the warmest on record for more than a century.

You can followLiveSciencewriter Wynne Parry on Twitter@Wynne_Parry. Follow LiveScience for the latest in science news and discoveries on Twitter@livescience and onFacebook.

© 2012 LiveScience.com. All rights reserved.

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