A new examination of temperatures in the United Statesshows that there were two times more heat records setin the past 20 years than cold ones.The Associated Press analyzed temperature informationcollected by 424 weather stations across the country.The analysis included temperature information from 1920 to 2008.It found that, most decades during the 20th centuryhad close to an even ratio of hot to cold records.But since 1999, 87 percent of the weather stationshad more hot records than cold.And, 42 stations reported having at leastfive hot records for every cold one since 1999.At 11 stations, the hot-to-cold ratioduring the period was 10-to-1 or greater.One place with the greatest difference in hot and cold recordswas the Southern California city of Pasadena.It went 19 years between cold records, the analysis found.It set a low temperature record last monthfor the first since June 5, 1999.Between those two record-cold days,Pasadena set 145 hot records.That included the city's all-time heat record of45 degrees Celsius set last year.The AP says it has shared its analysiswith experienced climate and data scientists.Several experts say results of the examinationsupport earlier scientific research.And, the information provides further evidencethat human-caused climate change has led tohigher temperatures over the years, the experts said.The use of such data is very important to identifyingthe long-term effects of climate change,climate scientist Deke Arndt told the Associated Press.He is the head of climate observation for the U.S. National Oceanicand Atmospheric Administration (NOAA).Arndt noted, for example, that the first two months of 2019showed twice as many cold records than hot ones- the exact opposite of the results in AP's analysis.However, he said such short-term differences are not as valuableas true climate trends measured over many years.Arndt said the AP analysis shows the United Stateshas been in a steady period of major warming for a long time.He added that this trend is expected to continue"to explore and break the warm end of the spectrummuch more than the cold end."Former Weather Channel expert Guy Waltonalso gave his thoughts on the findings.Walton, who has been studying hotand cold extreme records since 2000,told the AP he thinks the results show an unmistakable trend."You are getting more extremes.Your chances for getting more dangerous extremesare going up with time," he said.Arndt noted that such temperature extremescould have many different effects on people's lives.These include financial effects such as increased hospital stays,higher energy usage and farm losses.A recent study involving 22 U.S. states found that each summer,about 36,000 people seek hospital treatmentbecause of extreme heat.